A classification of chemical compounds according to certain chemical functional or structural properties.
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In chemistry, and especially in biochemistry, a fatty acid is a carboxylic acid with a long aliphatic tail (chain), which is either saturated or unsaturated. Most naturally occurring fatty acids have a chain of an even number of carbon atoms, from 4 to 28. Fatty acids are usually derived from triglycerides or phospholipids. When they are not attached to other molecules, they are known as "free" fatty acids. Fatty acids are important sources of fuel because, when metabolized, they yield large quantities of ATP. Many cell types can use either glucose or fatty acids for this purpose. In particular, heart and skeletal muscle prefer fatty acids. The brain cannot use fatty acids as a source of fuel; it relies on glucose or ketone bodies.
Fatty acids that have double bonds are known as unsaturated. Fatty acids without double bonds are known as saturated. They differ in length as well.
Fatty acid chains differ by length, often categorized as short to very long.
Unsaturated fatty acids have one or more double bonds between carbon atoms. (Pairs of carbon atoms connected by double bonds can be saturated by adding hydrogen atoms to them, converting the double bonds to single bonds. Therefore,
A homologous group of cyclic GLUCANS consisting of alpha-1,4 bound glucose units obtained by the action of cyclodextrin glucanotransferase on starch or similar substrates. The enzyme is produced by certain species of Bacillus. Cyclodextrins form inclusion complexes with a wide variety of substances.
A spiro compound is a bicyclic organic compound with rings connected through just one atom. The rings can be different in nature or identical. The connecting atom is also called the spiroatom, most often a quaternary carbon ("spiro carbon"). All spiro compounds have the infix spiro followed by square brackets containing the number of atoms in the smaller ring and the number of atoms in the larger ring excluding the spiroatom itself; the numbers being separated by a dot. For example compound A is called 1-bromo-3-chlorospiro[4.5]decan-7-ol and compound B is called 1-bromo-3-chlorospiro[3.6]decan-7-ol. The spiro compound consisting of a cyclohexane ring and a cyclopentane ring is called spiro[4.5]decane. This nomenclature was proposed by Adolf von Baeyer in 1900 .
An example of a spiro compound with a trivial name: spiropentadiene.
Acetals of cyclic ketones with diols or dithiols are spiro compounds. A example is Spirapril, with a five membered ring formed from 1,2-ethanedithiol.
A polyspiro compound is connected by two or more spiroatoms making up three or more rings.
When naming polyspiro compounds, the prefixes di-, tri-, tetra-, etc. are first added to the front of the name to
Chemicals of this type:2,4,5-Trichlorophenoxyacetic acid
Auxins are a class of plant hormones (or plant growth substances) with some morphogen-like characteristics. Auxins have a cardinal role in coordination of many growth and behavioral processes in the plant's life cycle and are essential for plant body development. Auxins and their role in plant growth were first described by the Dutch scientist Frits Went. Kenneth V. Thimann isolated this phytohormone and determined its chemical structure as indole-3-acetic acid. Went and Thiman then co-authored a book on plant hormones, Phytohormones, in 1937.
Auxins derive their name from the Greek word αυξειν (auxein - "to grow/increase"). They were the first of the major plant hormones to be discovered.
The (dynamic and to environment responsive) pattern of auxin distribution within the plant is a key factor for plant growth, its reaction to its environment, and specifically for development of plant organs (such as leaves or flowers). It is achieved through very complex and well coordinated active transport of auxin molecules from cell to cell throughout the plant body — by the so-called polar auxin transport. Thus, a plant can (as a whole) react to external conditions and adjust to them,
Metalloprotein is a generic term for a protein that contains a metal ion cofactor. A large fraction of all proteins are members of this category, so the area is very large.
It is estimated that approximately half of all proteins contain a metal. In another estimate, about one quarter to one third of all proteins are proposed require metals to carry out their functions. Thus, metalloproteins have many different functions in cells, such as enzymes, transport and storage proteins, and signal transduction proteins.
In metalloproteins, metal ions are usually coordinated by nitrogen, oxygen or sulfur centres belonging to amino acid residues of the protein. These donor groups are often provided by side-chains on the amino acid residues. Especially important are the imidazole substituent in histidine residues, thiolate substituents in cysteinyl residues, and carboxylate groups provided by aspartate. Given the diversity of the metalloproteome, virtually all amino acid residues have been shown to bind metal centers. The peptide backbone also provides donor groups, these include deprotonated amides and the amide carbonyl oxygen centres.
In addition to donor groups that are provided by amino
Sesquiterpene lactones are a class of chemical compounds; they are sesquiterpenoids (built from three isoprene units) and contain a lactone ring, hence the name. They are found in many plants and can cause allergic reactions and toxicity if overdosed, particularly in grazing livestock.
Sesquiterpene lactones can be divided into several main classes including germacranolides, heliangolides, guaianolides, pseudoguaianolides, hypocretenolides, and eudesmanolides.
Artemisinin, a new, highly-effective anti-malarial compound, is a sesquiterpene lactone found in Chinese wormwood. Lactucin, desoxylactucin, lactucopicrin, lactucin-15-oxalate, lactucopicrin-15-oxalate are some of the most prominent found in lettuce and spinach, giving most of the bitter taste to these crops.
One eudesmanolide, 3-oxo-5αH,8βH-eudesma-1,4(15),7(11)-trien-8,12-olide, can work with vernolic acid and other compounds in plants to reduce inflammation.
Some plants containing these compounds include:
A macrocycle is, as defined by IUPAC, "a cyclic macromolecule or a macromolecular cyclic portion of a molecule." In the chemical literature, organic chemists may consider any molecule containing a ring of nine or more atoms to be a macrocycle. Coordination chemists generally define a macrocycle more narrowly as a cyclic molecule with three or more potential donor atoms that can coordinate to a metal center.
The macrocyclic effect was discovered in 1969. Coordination chemists study macrocycles with three or more potential donor atoms in rings of greater than nine atoms as these compounds often have strong and specific binding with metals. This property of coordinating macrocyclic molecules is the macrocycle effect.
Macrocycles are generally synthesized from smaller, usually linear, molecules.
Macrocycles have been in use for several decades as synthetic dyes. Phthalocyanine is a porphyrin analogue, which is arguably the most useful, in uses as dyes and pigments since their discovery in 1928, due to their dark blue colour. There are however many other uses for them. Their name comes from their synthetic precursor, phthalodinitrile.
Chemicals of this type:Phospholipid-hydroperoxide glutathione peroxidase
Glutathione peroxidase (GPx) (EC 188.8.131.52) is the general name of an enzyme family with peroxidase activity whose main biological role is to protect the organism from oxidative damage. The biochemical function of glutathione peroxidase is to reduce lipid hydroperoxides to their corresponding alcohols and to reduce free hydrogen peroxide to water.
Several isozymes are encoded by different genes, which vary in celullar location and substrate specificity. Glutathione peroxidase 1 (GPx1) is the most abundant version, found in the cytoplasm of nearly all mammalian tissues, whose preferred substrate is hydrogen peroxide. Glutathione peroxidase 4 (GPx4) has a high preference for lipid hydroperoxides; it is expressed in nearly every mammalian cell, though at much lower levels. Glutathione peroxidase 2 is an intestinal and extracellular enzyme, while glutathione peroxidase 3 is extracellular, especially abundant in plasma. So far, eight different isoforms of glutathione peroxidase (GPx1-8) have been identified in humans.
An example reaction that glutathione peroxidase catalyzes is:
where GSH represents reduced monomeric glutathione, and GS–SG represents glutathione disulfide.
Sugar phosphates (sugars that have added or substituted phosphate groups) are often used in biological systems to store or transfer energy. They also form the backbone for DNA and RNA (DNA having two sugar molecules, and RNA having just one).
An aldose is a monosaccharide (a simple sugar) that contains only one aldehyde (-CH=O) group per molecule. The chemical formula takes the form Cn(H2O)n. The simplest possible aldose is the diose glycolaldehyde, which only contains two carbon atoms.
Because they have at least one asymmetric carbon centre, aldoses exhibit stereoisomerism. This means an aldose can exist in either a D form or L form of a Fischer projection. Biological systems tend to recognise D-aldoses more than L-aldoses.
An aldose differs from a ketose in that it has a carbonyl group at the end of the carbon chain instead of in the middle. This allows ketoses and aldoses to be chemically differentiated through Seliwanoff's test. An aldose may isomerize to a ketose through the Lobry-de Bruyn-van Ekenstein transformation.
Alkaline earths are the oxide of alkaline earth metals, namely lime, magnesia, strontia, baryta and beryllia. The alkaline earth metals are among the most electropositive of all metals, second only to the Group 1 or Alkali metals. Consequently, most of their compounds have a high degree of ionic character. This confers a high degree of basic nature to the oxides. On reacting with water, the corresponding hydroxides are obtained (in solution) which are strong bases. Although highly corrosive, they are used as antacids for their strongly basic nature.
Aluminum Acetate is a salt which can be produced by the reaction of aluminum hydroxide and acetic acid.
Molecular Formula: C6H9AlO6
The triacetate forms when aluminum sulfate is mixed with barium acetate. Another synthetic method is by bringing together aluminum hydroxide, acetic anhydride and glacial acetic acid in water, forming the basic aluminum monoacetate
The diacetate is prepared in a reaction of sodium aluminate (NaAlO2) with acetic acid.
A biogenic amine is a biogenic substance with one or more amine groups.
Some prominent examples of biogenic amines include:
There is a distinction between endogenous and exogenous biogenic amines. Endogenous amines are produced in many different tissues (for example: adrenaline in adrenal medulla or histamine in mast cells and liver). The amines are transmitted locally or via the blood system. The exogenous amines are directly absorbed from food in the intestine. Alcohol can increase the absorption rate. Monoamine oxidase (MAO) breaks down biogenic amines and prevents excessive resorption. MAO inhibitors (MAOIs) are also used as medications for the treatment of depression to prevent MAO from breaking down amines important for positive mood.
Monosaccharides (from Greek monos: single, sacchar: sugar) are the most basic units of biologically important carbohydrates. They are the simplest form of sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste. Examples of monosaccharides include glucose (dextrose), fructose (levulose), galactose, xylose and ribose. Monosaccharides are the building blocks of disaccharides such as sucrose and polysaccharides (such as cellulose and starch). Further, each carbon atom that supports a hydroxyl group (except for the first and last) is chiral, giving rise to a number of isomeric forms all with the same chemical formula. For instance, galactose and glucose are both aldohexoses, but have different chemical and physical properties.
With few exceptions (e.g., deoxyribose), monosaccharides have the chemical formula Cx(H2O)y, where x is at least 3. Monosaccharides can be classified by the number x of carbon atoms they contain: diose (2) triose (3) tetrose (4), pentose (5), hexose (6), heptose (7), and so on.
The most important monosaccharide, glucose, is a hexose. Examples of heptoses include the ketoses mannoheptulose and sedoheptulose.
Furan is a heterocyclic organic compound, consisting of a five-membered aromatic ring with four carbon atoms and one oxygen. The class of compounds containing such rings are also referred to as furans.
Furan is a colorless, flammable, highly volatile liquid with a boiling point close to room temperature. It is soluble in common organic solvents, including alcohol, ether and acetone, but is insoluble in water. It is toxic and may be carcinogenic. Furan is used as a starting point to other specialty chemicals.
The name furan comes from the Latin furfur, which means bran. The first furan derivative to be described was 2-furoic acid, by Carl Wilhelm Scheele in 1780. Another important derivative, furfural, was reported by Johann Wolfgang Döbereiner in 1831 and characterised nine years later by John Stenhouse. Furan itself was first prepared by Heinrich Limpricht in 1870, although he called it tetraphenol.
Industrially, furan is manufactured by the palladium-catalyzed decarbonylation of furfural, or by the copper-catalyzed oxidation of 1,3-butadiene:
In the laboratory, furan can be obtained from furfural by oxidation to furan-2-carboxylic acid, followed by decarboxylation. It can also be
In chemistry, a lactone is a cyclic ester which can be seen as the condensation product of an alcohol group -OH and a carboxylic acid group -COOH in the same molecule. It is characterized by a closed ring consisting of two or more carbon atoms and a single oxygen atom, with a ketone group =O in one of the carbons adjacent to the other oxygen.
Lactones are usually named according to the precursor acid molecule (aceto = 2 carbons, propio = 3, butyro = 4, valero = 5, capro = 6, etc.), with a -lactone suffix and a Greek letter prefix that specifies the number of carbons in the heterocyle — that is, the distance between the relevant -OH and the -COOH groups along said backbone. The first carbon atom after the carbon in the -COOH group on the parent compound is labelled α, the second will be labeled β, and so forth. Therefore, the prefixes also indicate the size of the lactone ring: α-lactone = 3-membered ring, β-lactone = 4-membered, γ-lactone = 5-membered, etc.
The other suffix used to denote a lactone is -olide, used in substance class names like butenolide, macrolide, cardenolide or bufadienolide.
The name lactone derives from the ring compound called lactide, which is formed from
Enzymes ( /ˈɛnzaɪmz/) are biological molecules that catalyze (i.e., increase the rates of) chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates sufficient for life. Since enzymes are selective for their substrates and speed up only a few reactions from among many possibilities, the set of enzymes made in a cell determines which metabolic pathways occur in that cell.
Like all catalysts, enzymes work by lowering the activation energy (Ea) for a reaction, thus dramatically increasing the rate of the reaction. As a result, products are formed faster and reactions reach their equilibrium state more rapidly. Most enzyme reaction rates are millions of times faster than those of comparable un-catalyzed reactions. As with all catalysts, enzymes are not consumed by the reactions they catalyze, nor do they alter the equilibrium of these reactions. However, enzymes do differ from most other catalysts in that they are highly specific for their substrates. Enzymes are known to catalyze about
In molecular biology a selenoprotein is any protein that includes a selenocysteine (Se-Cys) amino acid residue. Among functionally characterized selenoproteins are five glutathione peroxidases (GPX) and three thioredoxin reductases, (TrxR/TXNRD) which both contain only one Se-Cys. Selenoprotein P is the most common selenoprotein found in the plasma. It is unusual because in humans it contains 10 Se-Cys residues, which are split into two domains, a longer N-terminal domain that contains 1 Se-Cys, and a shorter C-terminal domain that contains 9 Se-Cys. The longer N-terminal domain is likely an enzymatic domain, and the shorter C-terminal domain is likely a means of safely transporting the very reactive Selenium atom throughout the body.
Selenoproteins exist in all major forms of life, eukaryotes, bacteria and archaea. Among eukaryotes, selenoproteins appear to be common in animals, but rare or absent in other phyla (one has been identified in the green alga Chlamydomonas, but none in other plants or in fungi). Among bacteria and archaea, selenoproteins are only present in some lineages, while they are completely absent in many other phylogenetic groups. These observations have
Galacto-oligosaccharides (GOS), also known as oligogalactosyllactose, oligogalactose, oligolactose or transgalactooligosaccharides (TOS), belong, because of their indigestible nature, to the group of prebiotics.
Organothiophosphates are organic compounds that include a phosphorus-sulfur bond.
Many of these compounds are quite toxic, and some are used as pesticides. Examples of these include:
However, several others have medical uses, including:
Xanthophylls (originally phylloxanthins) are yellow pigments that form one of two major divisions of the carotenoid group. The name is from Greek xanthos (ξανθος, "yellow") + phyllon (φύλλον, "leaf"), due to their formation of the yellow band seen in early chromatography of leaf pigments. Their molecular structure is similar to carotenes, which form the other major carotenoid group division, but xanthophylls contain oxygen atoms, while carotenes are purely hydrocarbons with no oxygen. Xanthophylls contain their oxygen either as hydroxyl groups and/or as pairs of hydrogen atoms that are substituted by oxygen atoms acting as a bridge (epoxide). For this reason, they are more polar than the purely hydrocarbon carotenes, and it is this difference that allows their separations from carotenes in many types of chromatography. Typically, carotenes are more orange in color than xanthophylls.
Like other carotenoids, xanthophylls are found in highest quantity in the leaves of most green plants, where they act to modulate light energy and perhaps serve as a non-photochemical quenching agent to deal with triplet chlorophyll (an excited form of chlorophyll), which is overproduced at high light
An essential amino acid or indispensable amino acid is an amino acid that cannot be synthesized de novo by the organism (usually referring to humans), and therefore must be supplied in the diet.
(*) Essential only in certain cases.
(**) Pyrrolysine, sometimes considered "the 22nd amino acid", is not listed here as it is not used by humans.
The amino acids regarded as essential for humans are phenylalanine, valine, threonine, tryptophan, isoleucine, methionine, leucine, lysine, and histidine. Additionally, cysteine (or sulphur-containing amino acids), tyrosine (or aromatic amino acids), and arginine are required by infants and growing children. Essential amino acids are "essential" not because they are more important to life than the others, but because the body does not synthesize them. They must be present in the the diet or they will not be present in the body. In addition, the amino acids arginine, cysteine, glycine, glutamine, histidine, proline, serine and tyrosine are considered conditionally essential, meaning they are not normally required in the diet, but must be supplied exogenously to specific populations that do not synthesize them in adequate amounts. An example would
In almost all known compounds of oxygen, the oxidation state of oxygen is -2. The oxidation state -1 is found in a few compounds such as peroxide. Compounds containing oxygen in other oxidation states are very uncommon: -1/2 (superoxide),-1/3 (ozonide), 0 (elemental, hypofluorous acid), +1/2 (dioxygenyl), +1 (dioxygen difluoride) and +2 (oxygen difluoride). The most familiar oxygen-containing compound is HO. Other well-known examples include silica (found in sand, glass, rock, etc.), and the compounds of carbon and oxygen, such as carbon dioxide (CO), alcohol (R-OH), carbonyl, (R-CO-H or R-CO-R), and carboxylic acid (R-COOH). Oxygenated radical such as chlorate (ClO), perchlorate (ClO), chromate (CrO), dichromate (CrO), permanganate (MnO), and nitrate (NO) are strong oxidizing agents in and of themselves. Phosphorus is biologically important in its oxygenated form as the phosphate (PO) ion. Many metals bond with oxygen atoms, such as iron in iron(III) oxide (FeO), commonly called rust.
There are known compounds of oxygen with almost all the other elements occurring in nature. The list of known compounds of oxygen includes some of the rarest elements: technetium (TcO),
The sulfur oxoacids are chemical compounds that contain sulfur, oxygen and hydrogen. The best known and most important industrially is sulfuric acid. Sulfur has a number of oxoacids; however, some of these are known only from their salts (these are shown in italics in the table below). The acids that have been characterised contain a variety of structural features, for example:
Oxepin is an oxygen-containing heterocycle consisting of a seven-membered ring with three double bonds. It exists as an equilibrium mixture with benzene oxide. The oxepin-benzene oxide system has fluctuating bonds in which the equilibrium can be shifted to one extreme or the other by suitable substituents. This compound is not aromatic.
An aldehyde ( /ˈældɨhaɪd/) is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center (a carbon double bonded to oxygen) bonded to hydrogen and an R group, which is any generic alkyl or side chain. The group without R is called the aldehyde group or formyl group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than between two carbon atoms. Aldehydes are common in organic chemistry. Many fragrances are aldehydes.
Aldehydes feature an sp-hybridized, planar carbon center that is connected by a double bond to oxygen and a single bond to hydrogen. The C-H bond is not acidic. Because of resonance stabilization of the conjugate base, an α-hydrogen in an aldehyde (not shown in the picture above) is far more acidic, with a pKa near 17, than a C-H bond in a typical alkane (pKa about 50). This acidification is attributed to (i) the electron-withdrawing quality of the formyl center and (ii) the fact that the conjugate base, an enolate anion, delocalizes its negative charge. Related to (i), the aldehyde group is somewhat polar.
Aldehydes (except those without an alpha
The chlorate anion has the formula ClO-
3. In this case, the chlorine atom is in the +5 oxidation state. "Chlorate" can also refer to chemical compounds containing this anion; chlorates are the salts of chloric acid. "Chlorate", when followed by a roman numeral in parentheses, e.g. chlorate(VII), refers to a particular oxyanion of chlorine.
As predicted by VSEPR, chlorate anions have trigonal pyramidal structures.
Chlorates are powerful oxidizers and should be kept away from organics or easily oxidized materials. Mixtures of chlorate salts with virtually any combustible material (sugar, sawdust, charcoal, organic solvents, metals, etc.) will readily deflagrate. Chlorates were once widely used in pyrotechnics for this reason, though their use has fallen due to their instability. Most pyrotechnic applications which formerly used chlorates in the past now use the more stable perchlorates instead.
The chlorate ion cannot be satisfactorily represented by just one Lewis structure, since all the Cl-O bonds are the same length (1.49 Å in potassium chlorate), and the chlorine atom is hypervalent. Instead, it is often thought of as a hybrid of multiple resonance structures:
In chemistry, an alcohol is an organic compound in which the hydroxyl functional group (-OH) is bound to a carbon atom. In particular, this carbon center should be saturated, having single bonds to three other atoms.
An important class of alcohols are the simple acyclic alcohols, the general formula for which is CnH2n+1OH. Of those, ethanol (C2H5OH) is the type of alcohol found in alcoholic beverages, and in common speech the word alcohol refers specifically to ethanol.
Other alcohols are usually described with a clarifying adjective, as in isopropyl alcohol (propan-2-ol) or wood alcohol (methyl alcohol, or methanol). The suffix -ol appears in the IUPAC chemical name of all substances where the hydroxyl group is the functional group with the highest priority; in substances where a higher priority group is present the prefix hydroxy- will appear in the IUPAC name. The suffix -ol in non-systematic names (such as paracetamol or cholesterol) also typically indicates that the substance includes a hydroxyl functional group and, so, can be termed an alcohol. But many substances, particularly sugars (examples glucose and sucrose) contain hydroxyl functional groups without using the
An electron acceptor is a chemical entity that accepts electrons transferred to it from another compound. It is an oxidizing agent that, by virtue of its accepting electrons, is itself reduced in the process.
Typical oxidizing agents undergo permanent chemical alteration through covalent or ionic reaction chemistry, resulting in the complete and irreversible transfer of one or more electrons. In many chemical circumstances, however, the transfer of electronic charge from an electron donor may be only fractional, meaning an electron is not completely transferred, but results in an electron resonance between the donor and acceptor. This leads to the formation of charge transfer complexes in which the components largely retain their chemical identities.
The electron accepting power of an acceptor molecule is measured by its electron affinity which is the energy released when filling the lowest unoccupied molecular orbital (LUMO).
The overall energy balance (ΔE), i.e., energy gained or lost, in an electron donor-acceptor transfer is determined by the difference between the acceptor's electron affinity (A) and the ionization potential (I) of the electron donor:
In chemistry, a class of
A polymer is a chemical compound or mixture of compounds consisting of repeating structural units created through a process of polymerization. The term derives from the ancient Greek word πολύς (polus, meaning "many, much") and μέρος (meros, meaning "parts"), and refers to a molecule whose structure is composed of multiple repeating units, from which originates a characteristic of high relative molecular mass and attendant properties. The units composing polymers derive, actually or conceptually, from molecules of low relative molecular mass. The term was coined in 1833 by Jöns Jacob Berzelius, though with a definition distinct from the modern IUPAC definition. Polymers are studied in the fields of biophysics and macromolecular science, and polymer science (which includes polymer chemistry and polymer physics). Historically, products arising from the linkage of repeating units by covalent chemical bonds have been the primary focus of polymer science; emerging important areas of the science now focus on non-covalent links. Because of the stipulation as to repeating substructures, polymers are formally a subclass of the category of macromolecules; the polyisoprene of latex rubber and
Volatile organic compounds (VOCs) are organic chemicals that have a high vapor pressure at ordinary, room-temperature conditions. Their high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate or sublimate from the liquid or solid form of the compound and enter the surrounding air. An example is formaldehyde, with a boiling point of –19 °C (–2 °F), slowly exiting paint and getting into the air.
VOCs are numerous, varied, and ubiquitous. They include both human-made and naturally occurring chemical compounds. Most scents or odors are of VOCs. VOCs play an important role in communication between plants. Some VOCs are dangerous to human health or cause harm to the environment. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Harmful VOCs are typically not acutely toxic, but instead have compounding long-term health effects. Because the concentrations are usually low and the symptoms slow to develop, research into VOCs and their effects is difficult.
Diverse definitions of the term VOC are in use.
The definitions of VOCs used for control of precursors of photochemical smog used by EPA,
Chloroalkyl ethers are a class of organic compounds with the general structure R-O-(CH2)n-Cl, characterized as an ether connected to a chloromethyl group via a alkane chain.
Chloromethyl methyl ether (CMME) is an ether with the formula CH3OCH2Cl. It is used as an alkylating agent and industrial solvent to manufacture dodecylbenzyl chloride, water repellents, ion-exchange resins, polymers, and as a chloromethylation reagent. It is a known human carcinogen. In organic synthesis the compound is used for the introduction of the methoxymethyl (MOM) protecting group.
Closely related compounds of industrial importance are bis(chloromethyl ether) (BCME) (closely related to chemical weapon sulfur mustard) and benzyl chloromethyl ether (BOMCl).
Methyl chloromethyl ether (often abbreviated MOMCl) is used as a protecting group for alcohols. The product formed is a MOM ether. A base such as N,N-diisopropylethylamine is a requirement.
The MOM group can be removed by application of dilute acid.
An example is the protection of a phenol group:
With a benzyl group the protective group becomes a BOM-ether. See also the closely related methylthiomethyl ethers.
A t-butyl group can also be used. The
Ethers ( /ˈiːθər/) are a class of organic compounds that contain an ether group — an oxygen atom connected to two alkyl or aryl groups — of general formula R–O–R'. A typical example is the solvent and anesthetic diethyl ether, commonly referred to simply as "ether" (CH3-CH2-O-CH2-CH3). Ethers are common in organic chemistry and pervasive in biochemistry, as they are common linkages in carbohydrates and lignin.
Ethers feature C-O-C linkage defined by a bond angle of about 104.5° and C-O distances of about 140 pm. The barrier to rotation about the C-O bonds is low. The bonding of oxygen in ethers, alcohols, and water is similar. In the language of valence bond theory, the hybridization at oxygen is sp.
Oxygen is more electronegative than carbon, thus the hydrogens alpha to ethers are more acidic than in simple hydrocarbons. They are far less acidic than hydrogens alpha to carbonyl groups (such as in ketones or aldehydes), however.
1) Simple ethers or symmetrical ethers 2) Mixed ethers or asymmetrical ethers
The names for simple ethers (i.e. those with none or few other functional groups) are a composite of the two substituents followed by "ether." Ethyl methyl ether (CH3OC2H5),
FODMAPs are short chain carbohydrates and monosaccharides which are poorly absorbed in the small intestine, including fructans, galactans, fructose and polyols. The term is an acronym, deriving from "Fermentable, Oligo-, Di-, Mono-saccharides and Polyols".
The restriction of FODMAPs from the diet has been found to have a beneficial effect for sufferers of irritable bowel syndrome and other functional gut disorders. The low FODMAP diet was developed at Monash University in Melbourne.
Poor absorption of most FODMAP carbohydrates is common to everyone. Any FODMAPs that are not absorbed in the small intestine pass into the large intestine, where the bacteria present ferment them. The resultant production of gas potentially results in bloating and flatulence. Most individuals do not suffer significant symptoms but some may suffer the symptoms of IBS. Restriction of FODMAP intake in the latter group has been found to result in improvement of symptoms.
Fructose malabsorption and lactose intolerance may produce IBS symptoms through the same mechanism but, unlike with other FODMAPs, poor absorption is found only in a minority of people. Many who benefit from a low FODMAP diet need not
Keratin (/ˈkɛrətən/) is a family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble and form strong unmineralized tissues found in reptiles, birds, amphibians, and mammals. The only other biological matter known to approximate the toughness of keratinized tissue is chitin.
Keratin derives from Greek κέρατος the genitive form of κέρας meaning "horn" from Proto-Indo-European *ḱer- of the same meaning.
Keratin filaments are abundant in keratinocytes in the cornified layer of the epidermis; these are cells which have undergone keratinization. In addition, keratin filaments are present in epithelial cells in general. For example, mouse thymic epithelial cells (TECs) are known to react with antibodies for keratin 5, keratin 8, and keratin 14. These antibodies are used as fluorescent markers to distinguish subsets of TECs in genetic studies of the thymus.
The baleen plates of filter-feeding whales are made of keratin.
Although it is now difficult to be certain, the
Sugar is the generalised name for a class of sweet-flavored substances used as food. They are carbohydrates and as this name implies, are composed of carbon, hydrogen and oxygen. There are various types of sugar derived from different sources. Simple sugars are called monosaccharides and include glucose, fructose and galactose. The table or granulated sugar most customarily used as food is sucrose, a disaccharide. Other disaccharides include maltose and lactose.
Sugars are found in the tissues of most plants but are only present in sufficient concentrations for efficient extraction in sugarcane and sugar beet. Sugarcane is a giant grass and has been cultivated in tropical climates in the Far East since ancient times. A great expansion in its production took place in the 18th century with the setting up of sugar plantations in the West Indies and Americas. This was the first time that sugar became available to the common people who had previously had to rely on honey to sweeten foods. Sugar beet is a root crop and is cultivated in cooler climates and became a major source of sugar in the 19th century when methods for extracting the sugar became available. Sugar production and trade
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond. The simplest acyclic alkenes, with only one double bond and no other functional groups, form an homologous series of hydrocarbons with the general formula CnH2n.
The simplest alkene is ethylene (C2H4), which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. Alkenes are also called olefins (an archaic synonym, widely used in the petrochemical industry). For bridged alkenes, the Bredt's rule states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough. Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes.
Like single covalent bonds, double bonds can be described in terms of overlapping atomic orbitals, except that, unlike a single bond (which consists of a single sigma bond), a carbon-carbon double bond consists of one sigma bond and one pi bond. This double bond is stronger than a single covalent bond (611 kJ/mol for C=C vs. 347 kJ/mol for C—C) and also shorter with
An aromatic amine is an amine with an aromatic substituent - that is -NH2, -NH- or nitrogen group(s) attached to an aromatic hydrocarbon, whose structure usually contains one or more benzene rings. Aniline is the simplest example.
Aromatic amines, when protonated, usually have lower pKa's (are more acidic) than their non-aromatic analogs. This is due to the delocalization of the lone pair of electrons from the nitrogen into the ring.
The general population is exposed to aromatic amines through the diet (e.g. pesticides), pharmaceuticals (e.g. prilocain), hair dyes, smoking, diesel engine exhaust as well as through occupational exposure at the workplace (e.g. rubber, textiles, dye industries).
Since August 2012, the new standard EN 14362-1:2012 Textiles - Methods for determination of certain aromatic amines derived from azo colorants - Part 1: Detection of the use of certain azo colorants accessible with and without extracting the fibres is effective. It had been officially approved by the European Committee for Standardization (CEN) and supersedes the test standards EN 14362-1: 2003 and EN 14362-2: 2003.
The standard describes a procedure to detect EU banned aromatic amines derived
Carotenoids are tetraterpenoid organic pigments that are naturally occurring in the chloroplasts and chromoplasts of plants and some other photosynthetic organisms like algae, some bacteria, and some types of fungus. Carotenoids can be synthesized from fats and other basic organic metabolic building blocks by all these organisms. Carotenoids generally cannot be manufactured by species in the animal kingdom (although one species of aphid is known to have acquired the genes for synthesis of the carotenoid torulene from fungi by horizontal gene transfer). Animals obtain carotenoids in their diets, and may employ them in various ways in metabolism.
There are over 600 known carotenoids; they are split into two classes, xanthophylls (which contain oxygen) and carotenes (which are purely hydrocarbons, and contain no oxygen). Carotenoids in general absorb blue light. They serve two key roles in plants and algae: they absorb light energy for use in photosynthesis, and they protect chlorophyll from photodamage. In humans, four carotenoids (beta-carotene, alpha-carotene, gamma-carotene, and beta-cryptoxanthin) have vitamin A activity (meaning they can be converted to retinal), and these and
Polyester resins are unsaturated resins formed by the reaction of dibasic organic acids and polyhydric alcohols. Polyester resins are used in sheet moulding compound, bulk moulding compound and the toner of laser printers. Wall panels fabricated from polyester resins reinforced with fiberglass — so-called fiberglass reinforced plastic (FRP) — are typically used in restaurants, kitchens, restrooms and other areas that require washable low-maintenance walls.
Unsaturated polyesters are condensation polymers formed by the reaction of polyols (also known as polyhydric alcohols), organic compounds with multiple alcohol or hydroxy functional groups, with saturated or unsaturated dibasic acids. Typical polyols used are glycols such as ethylene glycol; acids used are phthalic acid and maleic acid. Water, a by-product of esterification reactions, is continuously removed, driving the reaction to completion. The use of unsaturated polyesters and additives such as styrene lowers the viscosity of the resin. The initially liquid resin is converted to a solid by cross-linking chains. This is done by creating free radicals at unsaturated bonds, which propagate in a chain reaction to other
A valerate (compound) is a salt or ester of valeric acid. The valerate ion is C4H9COO (valeric acid minus one hydrogen ion).
Many steroid-based pharmaceuticals, for example ones based on betamethasone or hydrocortisone, include the steroid as the valerate ester.
An aromatic hydrocarbon or arene (or sometimes aryl hydrocarbon) is a hydrocarbon with alternating double and single bonds between carbon atoms forming rings. The term 'aromatic' was assigned before the physical mechanism determining aromaticity was discovered, and was derived from the fact that many of the compounds have a sweet scent. The configuration of six carbon atoms in aromatic compounds is known as a benzene ring, after the simplest possible such hydrocarbon, benzene. Aromatic hydrocarbons can be monocyclic (MAH) or polycyclic (PAH).
Some non-benzene-based compounds called heteroarenes, which follow Hückel's rule, are also aromatic compounds. In these compounds, at least one carbon atom is replaced by one of the heteroatoms oxygen, nitrogen, or sulfur. Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes an oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one nitrogen atom.
Benzene, C6H6, is the simplest aromatic hydrocarbon and was recognized as the first aromatic hydrocarbon, with the nature of its bonding first being recognized by Friedrich August
In chemistry, a coordination complex or metal complex, consists of an atom or ion (usually metallic), and a surrounding array of bound molecules or anions, that are in turn known as ligands or complexing agents. Many metal-containing compounds consist of coordination complexes.
Coordination complexes are so pervasive that the structure and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central atom or ion is called the donor atom. A typical complex is bound to several donor atoms, which can be the same or different. Polydentate (multiple bonded) ligands consist of several donor atoms, several of which are bound to the central atom or ion. These complexes are called chelate complexes, the formation of such complexes is called chelation, complexation, and coordination.
The central atom or ion, together with all ligands comprise the coordination sphere. The central atoms or ion and the donor atoms comprise the first coordination sphere.
Coordination refers to the "coordinate covalent bonds" (dipolar bonds) between the ligands and the central atom. Originally, a complex implied a reversible association of molecules, atoms, or
Scleroproteins, or fibrous proteins, constitute one of the three main classes of proteins, alongside globular proteins and conjugated proteins.
Keratin, collagen, elastin, and fibroin are all scleroproteins. The roles of such proteins include protection and support, forming connective tissue, tendons, bone matrices, and muscle fiber.
A scleroprotein forms long protein filaments, which are shaped like rods or wires. Scleroprotein are structural proteins or storage proteins that are typically inert and water-insoluble. A scleroprotein occurs as an aggregate due to hydrophobic side chains that protrude from the molecule.
A scleroprotein's peptide sequence often has limited residues with repeats; these can form unusual secondary structures, such as a collagen helix. The structures often feature cross-links between chains (e.g., cys-cys disulfide bonds between keratin chains).
Scleroproteins tend not to denature as easily as globular proteins.
Miroshnikov et al. (1998) are among the researchers who have attempted to synthesize fibrous proteins.
Microcystins are cyclic nonribosomal peptides produced by cyanobacteria (e.g.Microcystis aeruginosa and Planktothrix). They are cyanotoxins and can be very toxic for plants and animals including humans. Their hepatotoxicity may cause serious damage to the liver. Microcystins can strongly inhibit protein phosphatases type 1 (PP1) and 2A (PP2A), and are linked to pansteatitis.
Microcystins consist of several uncommon non-proteinogenic amino acids such as dehydroalanine derivatives and the special β-amino acid ADDA ((all-S,all-E)-3-Amino-9-methoxy-2,6,8-trimethyl-10-phenyldeca-4,6-diene acid).
Microcystin-LR is one of over 80 known toxic variants and is the most studied by chemists, pharmacologists, biologists and ecologists. Microcystin-containing 'blooms' are a problem worldwide, including China, Brazil, Australia, the United States and much of Europe. Once ingested, microcystin travels to the liver, via the bile acid transport system, where most is stored; though some remains in the blood stream and may contaminate tissue. Microcystin binds covalently to protein phosphatases thus disrupting cellular control processes.
There appears to be inadequate information to assess
A sulfonic acid (or sulphonic acid) refers to a member of the class of organosulfur compounds with the general formula RS(=O)2–OH, where R is an organic alkyl or aryl group and the S(=O)2–OH group a sulfonyl hydroxide. A sulfonic acid can be thought of as sulfuric acid with one hydroxyl group replaced by an organic substituent. The parent compound (with the organic substituent replaced by hydrogen) is the hypothetical compound sulfurous acid. Salts or esters of sulfonic acids are called sulfonates.
Sulfonic acid is produced by the process of sulfonation. Usually the sulfonating agent is sulfur trioxide. A particularly large scale application of this method is the production of alkylbenzenesulfonic acids:
In this reaction, sulfur trioxide is an electrophile and the arene undergoes electrophilic aromatic substitution.
Thiols can be oxidized to sulfonic acids:
Certain sulfonic acids, such as perfluorooctanesulfonic acid are prepared by electrophilic fluorination of preformed sulfonic acids. The net conversion can be represented simplistically:
Sulfonic acids are much stronger acids than the corresponding carboxylic acids. p-Toluenesulfonic acid, with a pKa of -2.8, is about a million
Gliadin is a glycoprotein present in wheat and several other cereals within the grass genus Triticum. Gliadins and glutens are essential for giving bread the ability to rise properly during baking.
Gliadins are prolamins and are separated on the basis of electrophoretic mobility and isoelectric focusing.
Gliadins are known for their role, along with glutenin, in the formation of gluten. They are slightly soluble in ethanol and contain only intramolecular disulfide links. They also cause some of the best examples of food-derived pathogenesis. People with gluten-sensitive enteropathy (the severe form of which is celiac disease) are sensitive to α, β, and γ gliadins. Those with WD urticaria and Baker's asthma are sensitive to ω-gliadins.
Gliadin can also serve as a useful delivery method for sensitive enzymes (such as superoxide dismutase, which is fused with gliadin to form glisodin) -- this helps protect them from stomach acids that cause breakdown.
For useful description of the gliadins see:
Deamidated gliadin is produced by acid or enzymatic treatment of gluten. The enzyme tissue transglutaminase converts some of the abundant glutamines to glutamic acid. This is done because
In chemistry, a divalent ion or molecule has a valence of two and thus can form two bonds with other ions or molecules. An older term for divalent is bivalent.
Divalent anions are atoms or radicals with two additional electrons when compared to their elemental state (that is, with 2 more electrons than protons). For instance, S is the sulfide anion.
A divalent cation is missing two electrons as compared with the neutral atom. For instance, iron(II) or Fe is the divalent cationic form of iron. Divalent cations are present in abundance in hard water, for example, calcium (Ca) and magnesium (Mg). These ionic minerals in solution are what contribute to the properties of water which cause it to be hard, such as the formation of limescale.
Flavan-3-ols (sometimes referred to as flavanols) are a class similar to flavonoids that use the 2-phenyl-3,4-dihydro-2H-chromen-3-ol skeleton. These compounds include the catechins and the catechin gallates.
Flavanols (with an "a") are not to be confused with flavonols (with an "o"), a class of flavonoids containing a ketone group.
The single-molecule (monomer) catechin, or isomer epicatechin (see diagram), adds four hydroxyls to flavan-3-ol, making building blocks for concatenated polymers (proanthocyanidins) and higher order polymers (anthocyanidins).
Flavanols possess two chiral carbons, meaning four diastereoisomers occur for each of them.
Catechins are distinguished from the yellow, ketone-containing flavonoids such as quercitin and rutin, which are called flavonols. Early use of the term bioflavonoid was imprecisely applied to include the flavanols, which are distinguished by absence of ketone(s). Catechin monomers, dimers, and trimers (oligomers) are colorless. Higher order polymers, anthocyanidins, exhibit deepening reds and become tannins.
The catechins are abundant in teas derived from the tea plant Camellia sinensis, as well as in some cocoas and chocolates (made from
Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to polypeptide side-chains. The carbohydrate is attached to the protein in a cotranslational or posttranslational modification. This process is known as glycosylation. Secreted extracellular proteins are often glycosylated. In proteins that have segments extending extracellularly, the extracellular segments are also glycosylated. Glycoproteins are often important integral membrane proteins, where they play a role in cell–cell interactions. Glycoproteins are also formed in the cytosol, but their functions and the pathways producing these modifications in this compartment are less well understood.
There are two types of glycoproteins:
Monosaccharides commonly found in eukaryotic glycoproteins include:
The sugar group(s) can assist in protein folding or improve proteins' stability.
One example of glycoproteins found in the body is mucins, which are secreted in the mucus of the respiratory and digestive tracts. The sugars attached to mucins give them considerable water-holding capacity and also make them resistant to proteolysis by digestive enzymes.
Glycoproteins are important for white blood
Phlorotannins are a type of tannins found in brown algae such as kelps and rockweeds or sargassacean species. Contrary to hydrolysable or condensed tannins, these compounds are oligomers of phloroglucinol (polyphloroglucinols).
These phenolic compounds are integral structural components of cell walls in brown algae , but they also seem to play many other secondary ecological roles such as protection from UV radiation and defense against grazing.
Most of the phlorotannins' biosynthesis is still unknown, but it appears they are formed from phloroglucinols via the acetate-malonate pathway.
They are found within the cell in small vesicles called physodes, where the soluble, polar fraction is sequestrated, and as part of the cell wall, where they are insoluble and act as a structural component. Their concentration is known to be highly variable among different taxa as well as among geographical area, since they respond plastically to a variety of environmental factors. Brown algaes also exsude phlorotannins in surrounding seawater.
It has been proposed that phlorotannins are first sequestered in physodes under their polar, reactive form before being oxidized and complexed to the alginic
Phytoalexins are antimicrobial substances synthesized de novo by plants that accumulate rapidly at areas of pathogen infection. They are broad spectrum inhibitors and are chemically diverse with different types characteristic of particular plant species. Phytoalexins tend to fall into several classes including terpenoids, glycosteroids and alkaloids; however, researchers often find it convenient to extend the definition to include all phytochemicals that are part of the plant's defensive arsenal.
Phytoalexins produced in plants act as toxins to the attacking organism. They may puncture the cell wall, delay maturation, disrupt metabolism or prevent reproduction of the pathogen in question. Their importance in plant defense is indicated by an increase in susceptibility of plant tissue to infection when phytoalexin biosynthesis is inhibited. Mutants incapable of phytoalexin production exhibit more extensive pathogen colonization as compared to wild type. As such, host-specific pathogens capable of degrading phytoalexins are more virulent than those unable to do so.
When a plant cell recognizes particles from damaged cells or particles from the pathogen, the plant launches a
Flavonoids (or bioflavonoids) (from the Latin word flavus meaning yellow, their colour in nature) are a class of plant secondary metabolites.
Flavonoids were referred to as Vitamin P (probably due to the effect they had on the permeability of vascular capillaries) from the mid-1930s to early 50s, but the term has since fallen out of use.
According to the IUPAC nomenclature, they can be classified into:
The three flavonoid classes above are all ketone-containing compounds, and as such, are flavonoids and flavonols. This class was the first to be termed "bioflavonoids." The terms flavonoid and bioflavonoid have also been more loosely used to describe non-ketone polyhydroxy polyphenol compounds which are more specifically termed flavanoids, flavan-3-ols (or catechins).
Flavonoids are widely distributed in plants fulfilling many functions.
Flavonoids are the most important plant pigments for flower coloration producing yellow or red/blue pigmentation in petals designed to attract pollinator animals.
In higher plants, Flavonoids are involved in UV filtration, symbiotic nitrogen fixation and floral pigmentation.
They may act as a chemical messenger or physiological regulator, they can
An oligosaccharide (from the Greek oligos, a few, and sacchar, sugar) is a saccharide polymer containing a small number (typically two to ten) of component sugars, also known as simple sugars (monosaccharides). Oligosaccharides can have many functions; for example, they are commonly found on the plasma membrane of animal cells where they can play a role in cell–cell recognition.
In general, they are found either O- or N-linked to compatible amino acid side-chains in proteins or to lipid moieties (see glycans).
Fructo-oligosaccharides (FOS), which are found in many vegetables, consist of short chains of fructose molecules. (Inulin has a much higher degree of polymerization than FOS and is a polysaccharide.) Galactooligosaccharides (GOS), which also occur naturally, consist of short chains of galactose molecules. These compounds can be only partially digested by humans.
Oligosaccharides are often found as a component of glycoproteins or glycolipids and as such are often used as chemical markers, often for cell recognition. An example is ABO blood type specificity. A and B blood types have two different oligosaccharide glycolipids embedded in the cell membranes of the red blood cells,
Platonic hydrocarbons are the molecular representation of platonic solid geometries with vertices replaced by carbon atoms and with edges replaced by chemical bonds. Not all platonic solids have an organic molecular counterpart:
The following platonic hydrocarbons, on the other hand, have been synthesised:
Tetrahedrane (C4H4) has not yet been synthesized, but it is predicted to be kinetically stable in spite of the acute bond angle and consequent angle strain. Tetrahedral hydrocarbons, including tetrahedrane with tert-butyl substituents and with trimethylsilyl substituents, have been produced.
With increasing number of carbon atoms in the frame, the geometry more closely approximates a sphere, and the space enclosed in the carbon "cage" increases. This trend continues with buckyballs or spherical fullerene (C60). Although not a hydrocarbon, fullerene has the shape of a truncated icosahedron, an Archimedean solid.
The propanoate or propionate ion is C2H5COO (propanoic acid minus one hydrogen ion).
A propanoic or propionic compound is a salt or ester of propanoic acid. In these compounds, propanoate is often written in shorthand, as CH3CH2CO2 or simply EtCO2.
Propanoates should not be confused with propenoates (commonly known as acrylates), the ions/salts/esters of propenoic acid (also known as 2-propenoic acid or acrylic acid).
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.
The dianion S exists only in strongly alkaline aqueous solutions. Such solutions can form by dissolution of H2S or alkali metal salts such as Li2S, Na2S, and K2S in the presence of extra hydroxide. The ion S is exceptionally basic with a pKa > 14. It does not exist in appreciable concentrations even in highly alkaline water, being undetectable at pH
A gallotannin is a class of molecules belonging to the hydrolysable tannins. Gallotannins are polymers formed when gallic acid, a polyphenol monomer, esterifies and binds with the hydroxyl group of a polyol carbohydrate such as glucose.
Gallate 1-beta-glucosyltransferase uses UDP-glucose and gallate to produce UDP and 1-galloyl-beta-D-glucose. Beta-glucogallin O-galloyltransferase uses 1-O-galloyl-beta-D-glucose to produce D-glucose and 1-O,6-O-digalloyl-beta-D-glucose. Beta-glucogallin-tetrakisgalloylglucose O-galloyltransferase uses 1-O-galloyl-beta-D-glucose and 1,2,3,6-tetrakis-O-galloyl-beta-D-glucose to produce D-glucose and 1,2,3,4,6-pentakis-O-galloyl-beta-D-glucose (1,2,3,4,6-penta-O-galloyl-β-D-glucose, the common precursor of gallotannins and the related ellagitannins).
Tannase is a key enzyme in tha degradation of gallotannins that uses digallic acid and H2O to produce gallic acid.
Polycyclic aromatic hydrocarbons (PAHs), also known as poly-aromatic hydrocarbons or polynuclear aromatic hydrocarbons, are potent atmospheric pollutants that consist of fused aromatic rings and do not contain heteroatoms or carry substituents. Naphthalene is the simplest example of a PAH. PAHs occur in oil, coal, and tar deposits, and are produced as byproducts of fuel burning (whether fossil fuel or biomass). As a pollutant, they are of concern because some compounds have been identified as carcinogenic, mutagenic, and teratogenic. PAHs are also found in cooked foods. Studies have shown that high levels of PAHs are found, for example, in meat cooked at high temperatures such as grilling or barbecuing, and in smoked fish. They are also found in the interstellar medium, in comets, and in meteorites and are a candidate molecule to act as a basis for the earliest forms of life. In graphene the PAH motif is extended to large 2D sheets.
Polycyclic aromatic hydrocarbons are lipophilic, meaning they mix more easily with oil than water. The larger compounds are less water-soluble and less volatile. Because of these properties, PAHs in the environment are found primarily in soil, sediment
Essential fatty acids, or EFAs, are fatty acids that humans and other animals must ingest because the body requires them for good health but cannot synthesize them. The term "essential fatty acid" refers to fatty acids required for biological processes, and not those that only act as fuel.
Only two EFAs are known for humans: alpha-linolenic acid (an omega-3 fatty acid) and linoleic acid (an omega-6 fatty acid). Other fatty acids that are only "conditionally essential" include gamma-linolenic acid (an omega-6 fatty acid), lauric acid (a saturated fatty acid), and palmitoleic acid (a monounsaturated fatty acid).
When the two EFAs were first discovered in 1923, they were designated Vitamin F. In 1930, work by Burr G.O., Burr M.M. and Miller E. on rats showed that the two EFAs are better classified with the fats than with the vitamins.
In the body, essential fatty acids serve multiple functions. In each of these, the balance between dietary ω-3 and ω-6 strongly affects function.
Fatty acids are straight chain hydrocarbons possessing a carboxyl (COOH) group at one end. The carbon next to the carboxylate is known as α, the next carbon β, and so forth. Since biological fatty acids can be
Condensed tannins (or polyflavonoid tannins, catechol-type tannins, pyrocatecollic type tannins, non-hydrolyzable tannins or flavolans) are polymers formed by the condensation of flavans. They do not contain sugar residues.
Different types of condensed tannins exist such as the proanthocyanidins, prodelphinidins, profisetinidins, proguibourtinidins or prorobinetidins.
Tannins of tropical woods tend to be of a cathetic nature rather than of the gallic type present in temperate woods.
One particular type of condensed tannin, found in grape are proanthocyanidins, which are polymers of 2 to 50 (or more) flavonoid units joined by carbon-carbon bonds. These are not susceptible to being cleaved by hydrolysis.
While hydrolyzable tannins and most condensed tannins are water soluble, some very large condensed tannins are insoluble.
Condensed tannins from Lithocarpus glaber leaves have a potent free radical scavenging activity. Condensed tannins can be found in Prunus sp.
Condensed tannins can be characterised by a number of techniques including depolymerisation, asymmetric flow field flow fractionation or small-angle X-ray scattering.
Depolymerisation reactions are mainly analytical
A ketohexose is a ketone-containing hexose (a six-carbon monosaccharide). The most common ketohexoses, each of which represents a pair of enantiomers (D- and L-isomers), include fructose, psicose, sorbose, and tagatose. Ketohexose is stable over a wide pH range, and with a primary pKa of 10.28, will only deprotonate at high pH, so is marginally less stable than aldohexose in solution.
Nonribosomal peptides (NRP) are a class of peptide secondary metabolites, usually produced by microorganisms like bacteria and fungi. Nonribosomal peptides are also found in higher organisms, such as nudibranchs, but are thought to be made by bacteria inside these organisms. While there exist a wide range of peptides that are not synthesized by ribosomes, the term nonribosomal peptide typically refers to a very specific set of these as discussed in this article.
Nonribosomal peptides are synthesized by nonribosomal peptide synthetases, which, unlike the ribosomes, are independent of messenger RNA. Each nonribosomal peptide synthetase can synthesize only one type of peptide. Nonribosomal peptides often have a cyclic and/or branched structures, can contain non-proteinogenic amino acids including D-amino acids, carry modifications like N-methyl and N-formyl groups, or are glycosylated, acylated, halogenated, or hydroxylated. Cyclization of amino acids against the peptide "backbone" is often performed, resulting in oxazolines and thiazolines; these can be further oxidized or reduced. On occasion, dehydration is performed on serines, resulting in dehydroalanine. This is just a sampling
Phenolic resin can include any of various synthetic thermosetting resins such as Bakelite, obtained by the reaction of phenols with simple aldehydes such as formaldehyde. Phenolics can be used to make molded products including pool balls, laboratory countertops, and as coatings and adhesives.
Phenolic material properties are useful in myriad industrial applications. Phenolic laminates are made by impregnating one or more layers of a base material such as paper, fiberglass or cotton with phenolic resin and laminating the resin-saturated base material under heat and pressure. The resin fully polymerizes (cures) during this process. The base material choice depends on the intended application of the finished product. Paper phenolics are used in manufacturing electrical components such as punch-through boards and household laminates. Glass phenolics are particularly well suited for use in the high speed bearing market. Phenolic micro-balloons are used for density control.
Reactive oxygen species (ROS) are chemically reactive molecules containing oxygen. Examples include oxygen ions and peroxides. Reactive oxygen species are highly reactive due to the presence of unpaired valence shell electrons. ROS form as a natural byproduct of the normal metabolism of oxygen and have important roles in cell signaling and homeostasis. However, during times of environmental stress (e.g., UV or heat exposure), ROS levels can increase dramatically. This may result in significant damage to cell structures. Cumulatively, this is known as oxidative stress. ROS are also generated by exogenous sources such as ionizing radiation.
Normally, cells defend themselves against ROS damage with enzymes such as alpha-1-microglobulin, superoxide dismutases, catalases, lactoperoxidases, glutathione peroxidases and peroxiredoxins. Small molecule antioxidants such as ascorbic acid (vitamin C), tocopherol (vitamin E), uric acid, and glutathione also play important roles as cellular antioxidants. In similar manner, polyphenol antioxidants assist in preventing ROS damage by scavenging free radicals. In contrast, the antioxidant ability of the extracellular space is less - e.g., the most
Polysaccharides are long carbohydrate molecules of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water.
When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans.
Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.
Polysaccharides have a general formula of Cx(H2O)y where x is usually a large number between 200 and 2500. Considering that the repeating units in the polymer backbone are often six-carbon monosaccharides, the general formula can also be represented as (C6H10O5)n where 40≤n≤3000.
Natural saccharides are generally built of simple carbohydrates called monosaccharides with general
An azole is a class of five-membered nitrogen heterocyclic ring compounds containing at least one other non-carbon atom of either nitrogen, sulfur, or oxygen. The parent compounds are aromatic and have two double bonds; there are successively reduced analogs (azolines and azolidines) with fewer. One, and only one, lone pair of electrons from each heteroatom in the ring is part of the aromatic bonding in an azole. Names of azoles maintain the prefix upon reduction (e.g., pyrazoline, pyrazolidine). The numbering of ring atoms in azoles starts with the heteroatom that is not part of a double bond, and then proceeds towards the other heteroatom.
(Six-membered aromatic heterocyclic systems with two nitrogens include pyrimidine and purine, important biochemicals.)
The azoles include:
A "dioxole" is a similar compound with two oxygen atoms in a five membered ring. Dioxolane is a derivative of dioxole.
Many azoles are used as antifungal drugs, inhibiting the fungal enzyme 14α-demethylase which produces ergosterol (an important component of the fungal plasma membrane).
Some people are allergic to azole(s).
Some azole drugs have adverse side-effects.
Some azole drugs may disrupt estrogen
Anthocyanidins are common plant pigments. They are the sugar-free counterparts of anthocyanins based on the flavylium ion or 2-phenylchromenylium, which is a type of oxonium ion (chromenylium is referred also to as benzopyrylium). They form a large group of polymethine dye. In particular anthocyanidins are salt derivatives of the 2-phenylchromenylium cation, also known as flavylium cation. As shown in the figure below, the phenyl group at the 2-position can carry different substituents. The counterion of the flavylium cation is mostly chloride. With this positive charge, the anthocyanidins differ from other flavonoids.
The stability of anthocyanidins is dependant on pH. At a low pH (acidic conditions), colored anthocyanidins are present, whereas at a higher pH (basic conditions) the colorless chalcones forms are present.
3-Deoxyanthocyanidins are a class of anthocyanidins lacking an hydroxyl group on carbon 3.
Chromate salts contain the chromate anion, CrO4. Dichromate salts contain the dichromate anion, Cr2O7. They are oxoanions of chromium in the oxidation state +6. They are moderately strong oxidizing agents.
Chromates react with hydrogen peroxide giving products in which peroxide, O2, replaces one or more oxygen atoms. In acid solution the unstable blue peroxo complex Chromium(VI) oxide peroxide, CrO(O2)2, is formed; it is an uncharged covalent molecule which may be extracted into ether. Addition of pyridine, results in the formation of the more stable complex CrO(O2)2py.
In aqueous solution, chromate and dichromate anions exist in a chemical equilibrium.
The predominance diagram shows that the position of the equilibrium depends on both pH and the analytical concentration of chromium. The chromate ion is the predominant species in alkaline solutions, but dichromate can become the predominant ion in acidic solutions. The change in colour with pH from yellow (chromate) to orange (dichromate) and the reversible nature of the equilibrium have been beautifully illustrated
Further condensation reactions can occur in strongly acidic solution with the formation of trichromates, Cr3O10, and
Most acids are weak acids. A weak acid is an acid that dissociates incompletely. It does not release all of its hydrogens in a solution, donating only a partial amount of its protons to the solution. These acids have higher pKa than strong acids, which release all of their hydrogen atoms when dissolved in water. Examples of weak acids include acetic acid (CH3COOH) and oxalic acid (H2C2O4).
Weak acids ionize in water solution to only a moderate extent; that is, if the acid was represented by the general formula HA, then in aqueous solution a significant amount of undissociated HA still remains. Weak acids in water dissociate as:
The strength of a weak acid is represented as either an equilibrium constant or as a percent dissociation. The equilibrium concentrations of reactants and products are related by the acid dissociation constant expression, (Ka):
The greater the value of Ka, the more the formation of H is favored, and the lower the pH of the solution. The Ka of weak acids varies between 1.8×10 and 55.5. Acids with a Ka less than 1.8×10 are weaker acids than water.
The other way to measure acid strength is to look at its percent dissociation, which is symbolized as α (alpha)
Alkynes are hydrocarbons that have a triple bond between two carbon atoms, with the formula CnH2n-2. Alkynes are traditionally known as acetylenes, although the name acetylene also refers specifically to C2H2, known formally as ethyne using IUPAC nomenclature. Like other hydrocarbons, alkynes are generally hydrophobic but tend to be more reactive.
Alkynes are characteristically more unsaturated than alkenes. Thus they add two equivalents of bromine whereas an alkene adds only one equivalent. Other reactions are listed below. Alkynes are usually more reactive than alkenes. They show greater tendency to polymerize or oligomerize than alkenes do. The resulting polymers, called polyacetylenes (which do not contain alkyne units) are conjugated and can exhibit semiconducting properties.
In acetylene, the H–C≡C bond angles are 180°. By virtue of this bond angle, alkynes tend to be rod-like. Correspondingly, cyclic alkynes are rare. Benzyne is highly unstable. The C≡C bond distance of 121 picometers is much shorter than the C=C distance in alkenes (134 pm) or the C-C bond in alkanes (153 pm).
The triple bond is very strong with a bond strength of 839 kJ/mol. The sigma bond contributes 369
A bromide is a chemical compound containing a bromide ion, that is a bromine atom with an effective charge of −1. The class name can include ionic compounds such as caesium bromide or covalent compounds such as sulfur dibromide.
Bromide is present in typical seawater (35 PSU) with a concentration of around 65 mg/L, which is around 0.2% of all dissolved salts. Seafoods and deep sea plants generally have high levels of bromide, while foods derived from land have variable amounts.
One can test for a bromide ion by adding dilute nitric acid (HNO3), then silver nitrate (AgNO3). A creamy precipitate of silver bromide forms.
Bromide compounds, especially potassium bromide, were frequently used as sedatives in the 19th and early 20th century. Their use in over-the-counter sedatives and headache remedies (such as Bromo-Seltzer) in the United States extended to 1975, when bromides were withdrawn as ingredients, due to chronic toxicity.
This use gave the word "bromide" its colloquial connotation of a boring cliché, a bit of conventional wisdom overused as a calming phrase, or verbal sedative.
The bromide ion is antiepileptic, and bromide salts are still used as such, particularly in
In chemistry, a disulfide usually refers to the structural unit composed of a linked pair of sulfur atoms. Disulfide usually refer to a chemical compound that contains a disulfide bond, such as diphenyl disulfide, C6H5S-SC6H5.
The disulfide anion is S2, or S–S. Sulfur is usually assigned to the reduced oxidation number −2, described as S and called sulfide. It has the electron configuration of a noble gas (argon). In disulfide, sulfur is only reduced to a state with oxidation number −1. Its configuration then resembles that of a chlorine atom. It thus tends to form a covalent bond with another S center to form S2 group. Oxygen also behaves similarly, e.g. in peroxides such as H2O2. Examples:
In many cases, each of the sulfur atoms in a disulfide group is covalently bonded to a carbon atom in an organic compound, forming a disulfide bond, sometimes called a disulfide linkage or a disulfide bridge. Examples:
Disulfide is also used to refer to compounds that contain two sulfide (S) centers. The compound carbon disulfide, CS2 is described with the structural formula i.e. S=C=S. This molecule is not a disulfide in the sense that it lacks a S-S bond. Similarly, molybdenum disulfide,
A pentose is a monosaccharide with five carbon atoms. Pentoses are organized into two groups. Aldopentoses have an aldehyde functional group at position 1. Ketopentoses have a ketone functional group in position 2 or 3.
The aldopentoses have three chiral centers and therefore eight different stereoisomers are possible.
The 2-ketopentoses have two chiral centers, and therefore four different stereoisomers are possible. The 3-ketopentoses are rare.
The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intramolecular hemiacetals and hemiketals, respectively. The resulting ring structure is related to furan, and is termed a furanose. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom — yielding two distinct configurations (α and β). This process is termed mutarotation.
Ribose is a constituent of RNA, and the related deoxyribose of DNA.
A polymer composed of pentose sugars is called a pentosan.
Phenol formaldehyde resins (PF) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Phenolic resins are mainly used in the production of circuit boards. They are better known however for the production of molded products including pool balls, laboratory countertops, and as coatings and adhesives. In the form of Bakelite, they are the earliest commercial synthetic resin.
Phenol-formaldehyde resins, as a group, are formed by a step-growth polymerization reaction that can be either acid- or base-catalysed. Since formaldehyde exists predominantly in solution as a dynamic equilibrium of methylene glycol oligomers, the concentration of the reactive form of formaldehyde depends on temperature and pH.
Phenol is reactive towards formaldehyde at the ortho and para sites (sites 2, 4 and 6) allowing up to 3 units of formaldehyde to attach to the ring. The initial reaction in all cases involves the formation of a hydroxymethyl phenol:
The hydroxymethyl group is capable of reacting with either another free ortho or para site, or with another hydroxymethyl group. The first reaction gives a methylene bridge, and the second forms an ether bridge:
The strength of an acid refers to its ability or tendency to lose a proton. There are very few strong acids. A strong acid is one that completely ionizes (dissociates) in water; in other words, one mole of a strong acid HA dissolves in water yielding one mole of H and one mole of the conjugate base, A. Essentially none of the non-ionized acid HA remains. In contrast a weak acid only partially dissociates, and at equilibrium both the acid and the conjugate base are present in solution. Examples of strong acids are hydrochloric acid (HCl), hydroiodic acid (HI), hydrobromic acid (HBr), perchloric acid (HClO4), nitric acid (HNO3) and sulfuric acid (H2SO4). In water each of these essentially ionizes 100%. The stronger an acid is, the more easily it loses a proton, H. Two key factors that contribute to the ease of deprotonation are the polarity of the H—A bond and the size of atom A, which determines the strength of the H—A bond. Acid strengths are also often discussed in terms of the stability of the conjugate base.
Stronger acids have a larger Ka and a more negative pKa than weaker acids.
Sulfonic acids, which are organic oxyacids, are a class of strong acids. A common example is
A carbohydrate is an organic compound that consists only of carbon, hydrogen, and oxygen, usually with a hydrogen:oxygen atom ratio of 2:1 (as in water); in other words, with the empirical formula Cm(H2O)n. (Some exceptions exist; for example, deoxyribose, a component of DNA, has the empirical formula C5H10O4.) Carbohydrates are not technically hydrates of carbon. Structurally it is more accurate to view them as polyhydroxy aldehydes and ketones.
The term is most common in biochemistry, where it is a synonym of saccharide. The carbohydrates (saccharides) are divided into four chemical groupings: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. In general, the monosaccharides and disaccharides, which are smaller (lower molecular weight) carbohydrates, are commonly referred to as sugars. The word saccharide comes from the Greek word σάκχαρον (sákkharon), meaning "sugar." While the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose. For example, blood sugar is the monosaccharide glucose, table sugar is the disaccharide sucrose, and milk sugar is the disaccharide lactose (see
Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic bonds.
Dextrins can be produced from starch using enzymes like amylases, as during digestion in the human body and during malting and mashing, or by applying dry heat under acidic conditions (pyrolysis or roasting). The latter process is used industrially, and also occurs on the surface of bread during the baking process, contributing to flavor, color, and crispness. Dextrins produced by heat are also known as pyrodextrins. During roasting under acid condition the starch hydrolyses and short chained starch parts partially rebranch with α-(1,6) bonds to the degraded starch molecule.
Dextrins are white, yellow, or brown powders that are partially or fully water-soluble, yielding optically active solutions of low viscosity. Most can be detected with iodine solution, giving a red coloration; one distinguishes erythrodextrin (dextrin that colours red) and achrodextrin (giving no colour).
White and yellow dextrins from starch roasted with little or no acid is called British gum.
Inositol phosphates are a group of mono- to polyphosphorylated inositols. They play crucial roles in diverse cellular functions, such as cell growth, apoptosis, cell migration, endocytosis, and cell differentiation. The group comprises:
Inositol trisphosphates act on the inositol triphosphate receptor to release calcium into the cytoplasm. Further reading: Function of calcium in humans
Inositol tetra-, penta-, and hexa-phosphates have been implicated in gene expression and Steger (both in Science Magazine).
An acid (from the Latin acidus/acēre meaning sour) is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH under 7, with acidity increasing the lower the pH. Chemicals or substances having the property of an acid are said to be acidic.
Common examples of acids include acetic acid (in vinegar), sulfuric acid (used in car batteries), and tartaric acid (used in baking). As these three examples show, acids can be solutions, liquids, or solids. Gases such as hydrogen chloride can be acids as well. Strong acids and some concentrated weak acids are corrosive, but there are exceptions such as carboranes and boric acid.
There are three common definitions for acids: the Arrhenius definition, the Brønsted-Lowry definition, and the Lewis definition. The Arrhenius definition states that acids are substances which increase the concentration of hydronium ions (H3O) in solution. The Brønsted-Lowry definition is an expansion: an acid is a substance which can act as a proton donor. Most acids encountered in everyday life are aqueous solutions, or can be dissolved in
Light-activated resins are one-part translucent polymers that cure and quickly harden when exposed to specific light spectrums. The required wavelength for cure is specific to the resin chemistry.
The resin remains liquid (thick, like syrup or honey) under normal indoor lighting which allows the user to work with the material until curing is desired. After curing, light-activated resin is denser than air-cured resins due to its inherent chemistry and because no mixing is required that might introduce air bubbles.
Resin chemistry is tailored by manufacturers to meet specific customer needs. Both visible light and ultraviolet light have been used as curing mechanisms for this technology. Ultraviolet light presents some potential hazards and workers using ultraviolet curing resins generally wear protective equipment.
Dentists have used visible-light activated resins as adhesives for decades. Resin cements are utilized in luting cast ceramic, full porcelain, and veneer restorations that are thin or translucent to permit visible light penetration and thus polymerize the cement. Light-activated cements may be radiolucent and are usually provided in various shades since they are utilized
A tannin (also known as vegetable tannin, natural organic tannins or sometimes tannoid, i.e. a type of biomolecule, as opposed to modern synthetic tannin) is an astringent, bitter plant polyphenolic compound that binds to and precipitates proteins and various other organic compounds including amino acids and alkaloids.
The term tannin (from tanna, an Old High German word for oak or fir tree, as in Tannenbaum) refers to the use of wood tannins from oak in tanning animal hides into leather; hence the words "tan" and "tanning" for the treatment of leather. However, the term "tannin" by extension is widely applied to any large polyphenolic compound containing sufficient hydroxyls and other suitable groups (such as carboxyls) to form strong complexes with proteins and other macromolecules.
The tannin compounds are widely distributed in many species of plants, where they play a role in protection from predation, and perhaps also as pesticides, and in plant growth regulation. The astringency from the tannins is what causes the dry and puckery feeling in the mouth following the consumption of unripened fruit or red wine. Likewise, the destruction or modification of tannins with time plays
A sugar alcohol (also known as a polyol, polyhydric alcohol, polyalcohol, or glycitol) is a hydrogenated form of carbohydrate, whose carbonyl group (aldehyde or ketone, reducing sugar) has been reduced to a primary or secondary hydroxyl group (hence the alcohol). Sugar alcohols have the general formula H(HCHO)n+1H, whereas sugars have H(HCHO)nHCO. In commercial foodstuffs sugar alcohols are commonly used in place of table sugar (sucrose), often in combination with high intensity artificial sweeteners to counter the low sweetness. Of these, xylitol is perhaps the most popular due to its similarity to sucrose in visual appearance and sweetness. Sugar alcohols do not contribute to tooth decay.
However, consumption of sugar alcohols does affect blood sugar levels. Sugar alcohols may also cause bloating and diarrhea when consumed in excessive amounts.
Some common sugar alcohols:
Both disaccharides and monosaccharides can form sugar alcohols; however, sugar alcohols derived from disaccharides (e.g. maltitol and lactitol) are not entirely hydrogenated because only one aldehyde group is available for reduction.
The simplest sugar alcohols, ethylene glycol and methanol, are sweet but
Substances that ionize into anions and cations in body fluids. Electrolytes regulate nerve and muscle function and water distribution between cells, plasma, and interstitial fluid. Imbalances can cause serious physiologic effects, including seizures, cardiac arrhythmias and convulsions.
Esters are chemical compounds consisting of a carbonyl adjacent to an ether linkage. They are derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH (hydroxyl) group is replaced by an -O-alkyl (alkoxy) group, and most commonly from carboxylic acids and alcohols. That is, esters are formed by condensing an acid with an alcohol.
Esters are ubiquitous. Most naturally occurring fats and oils are the fatty acid esters of glycerol. Esters with low molecular weight are commonly used as fragrances and found in essential oils and pheromones. Phosphoesters form the backbone of DNA molecules. Nitrate esters, such as nitroglycerin, are known for their explosive properties, while polyesters are important plastics, with monomers linked by ester moieties.
The word 'ester' was coined in 1848 by German chemist Leopold Gmelin, probably as a contraction of the German Essigäther - acetic ether.
Ester names are derived from the parent alcohol and the parent acid, where the latter may be an organic or an inorganic acid. Esters derived from the simplest carboxylic acids are commonly
Glycoconjugates is the general classification for carbohydrates covalently linked with other chemical species.
Glycoconjugates are very important compounds in biology and consist of many different categories such as glycoproteins, glycopeptides, peptidoglycans, glycolipids, and lipopolysaccharides. They are involved in cell–cell interactions, including cell–cell recognition, and cell–matrix interactions.
Formic acid (also called methanoic acid) is the simplest carboxylic acid. Its chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in the venom of bee and ant stings. In fact, its name comes from the Latin word for ant, formica, referring to its early isolation by the distillation of ant bodies. Esters, salts, and the anion derived from formic acid are referred to as formates.
Formic acid is a colorless liquid having a highly pungent, penetrating odor at room temperature. It is miscible with water and most polar organic solvents, and is somewhat soluble in hydrocarbons. In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules. Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law. Solid formic acid (two polymorphs) consists of an effectively endless network of hydrogen-bonded formic acid molecules. This relatively complicated compound also forms a low-boiling azeotrope with water (22.4%) and liquid formic acid also tends to supercool.
In nature, it is found in the stings and bites of many insects of the order
A hydrolyzable tannin or pyrogallol-type tannin is a type of tannin that, on heating with hydrochloric or sulfuric acids, yields gallic or ellagic acids.
At the center of a hydrolyzable tannin molecule, there is a carbohydrate (usually D-glucose but also cyclitols like quinic or shikimic acids). The hydroxyl groups of the carbohydrate are partially or totally esterified with phenolic groups such as gallic acid in gallotannins or ellagic acid in ellagitannins. Hydrolysable tannins are mixtures of polygalloyl glucoses and/or poly-galloyl quinic acid derivatives containing in between 3 up to 12 gallic acid residues per molecule.
Hydrolyzable tannins are hydrolyzed by weak acids or weak bases to produce carbohydrate and phenolic acids.
Examples of gallotannins are the gallic acid esters of glucose in tannic acid (C76H52O46), found in the leaves and bark of many plant species.
Tannins, including gallo and ellagic acid (epigallitannins), are inhibitors of HIV replication. 1,3,4-Tri-O-galloylquinic acid, 3,5-di-O-galloyl-shikimic acid, 3,4,5-tri-O-galloylshikimic acid, punicalin, punicalagin inhibited HIV replication in infected H9 lymphocytes with little cytotoxicity. Two compounds,
Unsaturated hydrocarbons are hydrocarbons that have double or triple covalent bonds between adjacent carbon atoms. Those with at least one double bond are called alkenes and those with at least one triple bond are called alkynes. Each double bond is represented by a number preceding the name of the base chain, representing on which hydrocarbon in the chain the double or triple bond can be found. Alkenes and alkynes with more than one double or triple bond respectively are named with the appropriate numeric prefix preceding the -ene or -yne.
Examples of unsaturated hydrocarbon include 2,4-pentadiene and 2-butyne, among others.
Unsaturated hydrocarbons with both double and triple bonds have the suffix -enyne and are handled in a similar manner.
The physical properties of unsaturated hydrocarbons are very similar to those of the corresponding saturated compounds. They are slightly soluble in water.
Except for aromatic compounds, unsaturated hydrocarbons are highly reactive and undergo addition reactions to their multiple bonds. Typical reagents added are hydrogen halides, water, sulfuric acid, elemental halogens and alcohols.
To test whether the hydrocarbon is unsaturated you should
Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines, trimethylamine, and aniline; see Category:Amines for a list of amines. Inorganic derivatives of ammonia are also called amines, such as chloramine (NClH2).
Compounds with the nitrogen atom attached to a carbonyl of the structure R–CO–NR′R″ are called amides and have different chemical properties from amines.
An aliphatic amine has no aromatic ring attached directly to the nitrogen atom. Aromatic amines have the nitrogen atom connected to an aromatic ring as in the various anilines. The aromatic ring decreases the alkalinity of the amine, depending on its substituents. The presence of an amine group strongly increases the reactivity of the aromatic ring, due to an electron-donating effect.
Amines are organized into four subcategories:
It is also possible to have four organic substituents on the nitrogen. These species are not amines but are quaternary ammonium cations and have a charged
Bridged compounds are compounds which contain interlocking rings.
The nomenclature of bridged compounds was established by the von Baeyer system. Some important concepts for bridged compounds are:
In chemistry, a glycoside /ˈɡlaɪkəsaɪd/ is a molecule in which a sugar is bound to a non-carbohydrate moiety, usually a small organic molecule. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. These can be activated by enzyme hydrolysis, which causes the sugar part to be broken off, making the chemical available for use. Many such plant glycosides are used as medications. In animals and humans, poisons are often bound to sugar molecules as part of their elimination from the body.
In formal terms, a glycoside is any molecule in which a sugar group is bonded through its anomeric carbon to another group via a glycosidic bond. Glycosides can be linked by an O- (an O-glycoside), N- (a glycosylamine), S-(a thioglycoside), or C- (a C-glycoside) glycosidic bond. The given definition is the one used by IUPAC, which recommends the Haworth projection to correctly assign stereochemical configurations. Many authors require in addition that the sugar be bonded to a non-sugar for the molecule to qualify as a glycoside, thus excluding polysaccharides. The sugar group is then known as the glycone and the non-sugar group as
An iodate is a conjugate base of iodic acid. In the iodate anion, iodine is bonded to three oxygen atoms and the molecular formula is IO3. The molecular geometry of iodate is trigonal pyramidal.
Iodate can be obtained by reducing periodate with a thioether. The byproduct of the reaction is a sulfoxide.
Iodates are a class of chemical compounds containing this group. Examples are sodium iodate (NaIO3), silver iodate (AgIO3), and calcium iodate (Ca(IO3)2). iodates resemble chlorates with iodine instead of chlorine.
In acid conditions, iodic acid is formed. Potassium hydrogen iodate (KH(IO3)2) is a double salt of potassium iodate and iodic acid and an acid as well. Iodates are used in the iodine clock reaction.
Peptides (from the Greek πεπτός, "digested" from πέσσειν "to digest") are short polymers of amino acid monomers linked by peptide bonds, the covalent chemical bonds formed between two molecules when the carboxyl group of one molecule reacts with the amino group of the other molecule. Peptides are distinguished from proteins on the basis of size, typically containing fewer than 50 monomer units. The shortest peptides are dipeptides, consisting of two amino acids joined by a single peptide bond. There are also tripeptides, tetrapeptides, etc.
Amino acids which have been incorporated into a peptide are termed "residues"; every peptide has a N-terminus and C-terminus residue on the ends of the peptide (except for cyclic peptides). A polypeptide is a long, continuous, and unbranched peptide. Proteins consist of one or more polypeptides arranged in a biologically functional way and are often bound to cofactors, or other proteins.
The size boundaries which distinguish peptides, polypeptides, and proteins are arbitrary. Long peptides such as amyloid beta can be considered proteins, whereas small proteins such as insulin can be considered peptides.
Peptides are divided into several classes,
Scavenger resins are polymers (resins) with bound functional groups that react with specific by-products, impurities, or excess reagents produced in a reaction. Polymer-bound functional groups permit the use of many different scavengers, as the functional groups are confined within a resin or are simply bound to the solid support of a bead. Simply, the functional groups of one scavenger will react minimally with the functional groups of another.
Employment of scavenger resins has become increasingly popular in solution-phase combinatorial chemistry. Used primarily in the synthesis of medicinal drugs, solution-phase combinatorial chemistry allows for the creation of large libraries of structurally related compounds. When purifying a solution, many approaches can be taken. In general chemical synthesis laboratories, a number of traditional techniques for purification are used as opposed to the employment of scavenger resins. Whether or not scavenger resins are used often depends on the quantity of product desired, how much time you have to produce the wanted product, and the use of the product. Some of the advantages and disadvantages to using scavenger resins as a means for
In organic chemistry, a thiol ( /ˈθaɪˌɒl/) is an organosulfur compound that contains a carbon-bonded sulfhydryl (–C–SH or R–SH) group (where R represents an alkane, alkene, or other carbon-containing group of atoms). Thiols are the sulfur analogue of alcohols (that is, sulfur takes the place of oxygen in the hydroxyl group of an alcohol), and the word is a portmanteau of "thio" + "alcohol," with the first word deriving from Greek θεῖον ("thion") = "sulfur". The –SH functional group itself is referred to as either a thiol group or a sulfhydryl group.
Many thiols have strong odors resembling that of garlic. Thiols are used as odorants to assist in the detection of natural gas (which in pure form is odorless), and the "smell of natural gas" is due to the smell of the thiol used as the odorant.
Thiols are often referred to as mercaptans. The term mercaptan is derived from the Latin mercurium captans (capturing mercury) because the thiolate group bonds so strongly with mercury compounds.
Thiols and alcohols have similar molecular structure. The major difference is the size of the chalcogenide, C–S bond lengths being around 180 picometers in length. The C–S–H angles approach 90°. In the
Sulfinic acids are oxoacids of sulfur with the structure RSO(OH). In these organosulfur compounds, sulfur is pyramidal.
They are often prepared in situ by acidification of the corresponding sulfinate salts, which are typically more robust than the acid. These salts are generate by reduction of sulfonyl chlorides. An alternative route is the reaction of Grignard reagents with sulfur dioxide. Transition metal sulfinates are also generated by insertion of sulfur dioxide into metal alkyls, a reaction that may proceeds via a metal sulfur dioxide complex.
An example of a simple, well-studied sulfinic acid is phenylsulfinic acid. A commercially important sulfinic acid is thiourea dioxide, which is prepared by the oxidation of thiourea with hydrogen peroxide.
Another commercially important sulfinic acid is hydroxymethyl derivative, which is usually employed as its sodium salt (HOCH2SO2Na). Called Rongalite, this anion is a commercially useful reducing agent.
Acid salt is a term for a class of salts formed by the partial neutralization of diprotic or polyprotic acids. Because the parent acid is only partially neutralized, one or more replaceable hydrogen atoms remain. Typical acid salts have one or more alkali (alkaline) metal ions as well as one or more hydrogen atoms. Well known examples are sodium bicarbonate (NaHCO3), sodium hydrosulfide (NaHS), sodium bisulfate (NaHSO4), monosodium phosphate (NaH2PO4), and disodium phosphate (Na2HPO4). Often acid salts are used as buffers.
For example, the acid salt sodium bisulfate is the main species formed upon the half neutralization of sulfuric acid with sodium hydroxide:
Acid salts compounds can act either as an acid or a base: addition of a suitably strong acid will protonate anions, and addition of a suitably strong base will split off H. The pH of a solution of an acid salt will depend on the relevant equilibrium constants and the amounts of any additional base or acid. A comparison between the Kb and Ka will indicate this: if Kb > Ka, the solution will be basic, whereas if Kb
Collagen ( /ˈkɒlədʒɨn/) is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of vertebrates. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content. Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendon, ligament and skin, and is also abundant in cornea, cartilage, bone, blood vessels, the gut, and intervertebral disc. The fibroblast is the most common cell which creates collagen.
In muscle tissue, it serves as a major component of the endomysium. Collagen constitutes one to two percent of muscle tissue, and accounts for 6% of the weight of strong, tendinous muscles. Gelatin, which is used in food and industry, is collagen that has been irreversibly hydrolyzed.
The molecular and packing structures of collagen have eluded scientists over decades of research. The first evidence that it possesses a regular structure at the molecular level was presented in the mid-1930s. Since that time, many prominent scholars, including Nobel laureates Crick, Pauling, Rich and Yonath, and others, including
Prolamins are a group of plant storage proteins having a high proline content and found in the seeds of cereal grains: wheat (gliadin), barley (hordein), rye (secalin), corn (zein), sorghum (kafirin) and as a minor protein, avenin in oats. They are characterised by a high glutamine and proline content and are generally soluble only in strong alcohol solutions. Some prolamins, notably gliadin, and similar proteins found in the tribe Triticeae (see Triticeae glutens) may induce coeliac disease in genetically predisposed individuals.
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations (positively charged ions) and anions (negative ions) so that the product is electrically neutral (without a net charge). These component ions can be inorganic such as chloride (Cl), as well as organic such as acetate (CH3COO) and monatomic ions such as fluoride (F), as well as polyatomic ions such as sulfate (SO4).
There are several varieties of salts. Salts that hydrolyze to produce hydroxide ions when dissolved in water are basic salts and salts that hydrolyze to produce hydronium ions in water are acid salts. Neutral salts are those that are neither acid nor basic salts. Zwitterions contain an anionic center and a cationic center in the same molecule but are not considered to be salts. Examples include amino acids, many metabolites, peptides, and proteins.
Molten salts and solutions containing dissolved salts (e.g., sodium chloride in water) are called electrolytes, as they are able to conduct electricity. As observed in the cytoplasm of cells, in blood, urine, plant saps and mineral waters, mixtures of many different ions in solution usually
Silicone resins are a type of silicone material which is formed by branched, cage-like oligosiloxanes with the general formula of RnSiXmOy, where R is a non reactive substituent, usually Me or Ph, and X is a functional group H, OH, Cl or OR. These groups are further condensed in many applications, to give highly crosslinked, insoluble polysiloxane networks.
When R is methyl, the four possible functional siloxane monomeric units are described as follows:
Note that a network of only Q groups becomes fused quartz.
The most abundant silicone resins are built of D and T units (DT resins) or from M and Q units (MQ resins), however many other combinations (MDT, MTQ, QDT) are also used in industry.
Silicone resins represent a broad range of products. Materials of molecular weight in the range of 1000-10 000 are very useful in pressure sensitive adhesives, silicone rubbers, coatings and additives.
Silicone resins are prepared by hydrolytic condensation of various silicone precursors. In early processes of preparation of silicone resins sodium silicate and various chlorosilanes were used as starting materials. Although the starting materials were the least expensive ones (something typical
In chemistry, an alkali ( /ˈælkəlaɪ/; from Arabic: al-qaly القلي, القالي ) is a basic, ionic salt of an alkali metal or alkaline earth metal element. Some authors also define an alkali as a base that dissolves in water. A solution of a soluble base has a pH greater than 7. The adjective alkaline is commonly used in English as a synonym for base, especially for soluble bases. This broad use of the term is likely to have come about because alkalis were the first bases known to obey the Arrhenius definition of a base and are still among the more common bases.
The word "alkali" is derived from Arabic al qalīy (or alkali), meaning the calcined ashes (see calcination), referring to the original source of alkaline substances. A water-extract of burned plant ashes, called potash and composed mostly of potassium carbonate, was mildly basic. After heating this substance with calcium hydroxide (slaked lime), a far more strongly basic substance known as caustic potash (potassium hydroxide) was produced. Caustic potash was traditionally used in conjunction with animal fats to produce soft soaps, one of the caustic processes that rendered soaps from fats in the process of saponification, known
The amyrins are a pair of closely related natural chemical compounds of the triterpene class. They are designated α-amyrin and β-amyrin. Each has the chemical formula C30H50O. They are widely distributed in nature and have been isolated from a variety of plant sources.
Phthalic acids, also known as benzene dicarboxylic acid, are organic acid with the chemical formula CH(COOH). There are three isomer: ortho- or phthalic acid (benzene-1,2-dicarboxylic acid); meta- or isophthalic acid (benzene-1,3-dicarboxylic acid); para- or terephthalic acid (benzene-1,4-dicarboxylic acid).
Inorganic compounds are of inanimate, not biological origin. Inorganic compounds lack carbon and hydrogen atoms and are synthesized by the agency of geological systems. In contrast, the synthesis of organic compounds in biological systems incorporates carbohydrates into the molecular structure. Organic chemists traditionally refer to any molecule containing carbon as an organic compound and by default this means that inorganic chemistry deals with molecules lacking carbon. However, biologists may distinguish organic from inorganic compounds in a different way that does not hinge on the presence of a carbon atom. Pools of organic matter, for example, that have been metabolically incorporated into living tissues persist in decomposing tissues, but as molecules become oxidized into the open environment, such as atmospheric CO2, this creates a separate pool of inorganic compounds. The distinction between inorganic and organic compounds is not always clear when dealing with open and closed systems, because everything is ultimately connected to everything else on the planet. Some scientists, for example, view the open environment (i.e., the ecosphere) as an extension of life and from
Pectin (from Greek πηκτικός – pektikos, "congealed, curdled") is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot. It is produced commercially as a white to light brown powder, mainly extracted from citrus fruits, and is used in food as a gelling agent particularly in jams and jellies. It is also used in fillings, medicines, sweets, as a stabilizer in fruit juices and milk drinks, and as a source of dietary fiber.
In plant cells, pectin consists of a complex set of polysaccharides (see below) that are present in most primary cell walls and are particularly abundant in the non-woody parts of terrestrial plants. Pectin is present not only throughout primary cell walls but also in the middle lamella between plant cells, where it helps to bind cells together.
The amount, structure and chemical composition of pectin differs among plants, within a plant over time, and in various parts of a plant. Pectin is an important cell wall polysaccharide that allows primary cell wall extension and plant growth. During fruit ripening, pectin is broken down by the enzymes pectinase and
Triterpenes are terpenes consisting of six isoprene units and have the molecular formula C30H48.
The pentacyclic triterpenes can be classified into lupane, oleanane or ursane groups.
A notable pentacyclic triterpene is Boswellic acid.
Animal- and plant-derived triterpenes exist, such as:
Triterpenoids are thought of as modified triterpenes, such as lanosterol.
An aldohexose is a hexose with an aldehyde group on one end.
The aldohexoses have four chiral centres for a total of 16 possible aldohexose stereoisomers (2). Of these, only three commonly occur in nature: D-glucose, D-galactose, and D-mannose. The D/L configuration is based on the orientation of the hydroxyl at position 5, and does not refer to the direction of optical activity.
There are eight D-aldohexoses:
The chemist Emil Fischer is said to have devised the following mnemonic device for remembering the order given above, which corresponds to the configurations about the chiral centers when ordered as 3-bit binary strings: All altruists gladly make gum in gallon tanks.
Aldohexoses can have one or more of their hydroxyl groups replaced by hydrogens to form deoxyaldohexoses. The following are well known cases of such compounds :
In chemistry, an amino sugar contains an amine group in place of a hydroxyl group. Derivatives of amine containing sugars, such as N-acetylglucosamine and sialic acid, while not formally containing an amine, are also considered amino sugars.
Aminoglycosides are a class of antimicrobial compounds that inhibit bacterial protein synthesis. These compounds are conjugates of amino sugars and aminocyclitols.
Common examples of amino sugars include:
Ankyrins are a family of adaptor proteins that mediate the attachment of integral membrane proteins to the spectrin-actin based membrane skeleton. Ankyrins have binding sites for the beta subunit of spectrin and at least 12 families of integral membrane proteins. This linkage is required to maintain the integrity of the plasma membranes and to anchor specific ion channels, ion exchangers and ion transporters in the plasma membrane.
Ankyrins contain four functional domains: an N-terminal domain that contains 24 tandem ankyrin repeats, a central domain that binds to spectrin, a death domain that binds to proteins involved in apoptosis, and a C-terminal regulatory domain that is highly variable between different ankyrin proteins.
Ankyrins are encoded by three genes (ANK1, ANK2 and ANK3) in mammals. Each gene in turn produces multiple proteins through alternative splicing.
The ANK1 gene encodes the AnkyrinR proteins. AnkyrinR was first characterized in human erythrocytes, where this ankyrin was referred to as erythrocyte ankyrin or band2.1. AnkyrinR enables erythrocytes to resist shear forces experienced in the circulation. Individuals with reduced or defective ankyrinR have a form of
In organic chemistry, an aryl halide (also known as haloarene or halogenoarene) is an aromatic compound in which one or more hydrogen atoms directly bonded to an aromatic ring are replaced by a halide. The haloarene are distinguished from haloalkanes because they exhibit many differences in methods of preparation and properties. The most important members are the aryl chlorides, but the class of compounds is so broad that many derivatives enjoy niche applications.
The two main preparatory routes to aryl halides are direct halogenation and via diazonium salts.
In the Friedel-Crafts halogenation, a Lewis acid serve as catalysts. Many metal chlorides are used, examples include iron(III) chloride or aluminium chloride. The most important aryl halide, chlorobenzene is produced by this route. Monochlorination of benzene is always accompanied by formation of the dichlorobenzene derivatives.
Arenes with electron donating groups react with halogens even in the absence of Lewis acids. For example, phenols and anilines react quickly with chlorine and bromine water to give multiply halogenated products. The decolouration of bromine water by electron-rich arenes is used in the bromine
Biopolymers are polymers produced by living organisms. Since they are polymers, biopolymers contain monomeric units that are covalently bonded to form larger structures. There are three main classes of biopolymers based on the differing monomeric units used and the structure of the biopolymer formed: polynucleotides, which are long polymers composed of 13 or more nucleotide monomers; polypeptides, which are short polymers of amino acids; and polysaccharides, which are often linear bonded polymeric carbohydrate structures.
Cellulose is the most common organic compound and biopolymer on Earth. About 33 percent of all plant matter is cellulose. The cellulose content of cotton is 90 percent and that of wood is 50 percent.
A major but defining difference between biopolymers and other polymers can be found in their structures. All polymers are made of repetitive units called monomers. Biopolymers often have a well-defined structure, though this is not a defining characteristic (example:ligno-cellulose): The exact chemical composition and the sequence in which these units are arranged is called the primary structure, in the case of proteins. Many biopolymers spontaneously fold into
Carboxylic acids ( /ˌkɑrbɒkˈsɪlɪk/) are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group. A carboxyl group (or carboxy) is a functional group consisting of a carbonyl (RR'C=O) and a hydroxyl (R-O-H), which has the formula -C(=O)OH, usually written as -COOH or -CO2H.
Carboxylic acids are Brønsted-Lowry acids because they are proton (H) donors. They are the most common type of organic acid. Among the simplest examples are formic acid H-COOH, which occurs in ants, and acetic acid CH3-COOH, which gives vinegar its sour taste. Acids with two or more carboxyl groups are called dicarboxylic, tricarboxylic, etc. The simplest dicarboxylic example is oxalic acid (COOH)2, which is just two connected carboxyls. Mellitic acid is an example of a hexacarboxylic acid. Other important natural examples are citric acid (in lemons) and tartaric acid (in tamarinds).
Salts and esters of carboxylic acids are called carboxylates. When a carboxyl group is deprotonated, its conjugate base, a carboxylate anion is formed. Carboxylate ions are resonance stabilized and this increased
In biochemistry, ligase (from the Latin verb ligāre — "to bind" or "to glue together") is an enzyme that can catalyze the joining of two large molecules by forming a new chemical bond, usually with accompanying hydrolysis of a small chemical group dependent to one of the larger molecules or the enzyme catalyzing the linking together of two compounds....e.g.: Enzymes which catalyze joining of C-O,C-S,C-N etc. .In general, a ligase catalyzes the following reaction:
where the lowercase letters signify the small, dependent groups.
The common names of ligase enzymes often include the word "ligase," such as DNA ligase, an enzyme commonly used in molecular biology laboratories to join together DNA fragments. Other common names for ligases include synthetases, because they are used to synthesize new molecules.
Note that, originally, biochemical nomenclature distinguished synthetases and synthases. Under the original definition, synthases do not use energy from nucleoside triphosphates (such as ATP, GTP, CTP, TTP, and UTP), whereas synthetases do use nucleoside triphosphates. It is also said that a synthase is a lyase (a lyase is an enzyme that catalyzes the breaking of various
An organic acid is an organic compound with acidic properties. The most common organic acids are the carboxylic acids, whose acidity is associated with their carboxyl group –COOH. Sulfonic acids, containing the group –SO2OH, are relatively stronger acids. Alcohols, with –OH, can act as acids but they are usually very weak. The relative stability of the conjugate base of the acid determines its acidity. Other groups can also confer acidity, usually weakly: the thiol group –SH, the enol group, and the phenol group. In biological systems, organic compounds containing these groups are generally referred to as organic acids.
A few common examples include:
In general, organic acids are weak acids and do not dissociate completely in water, whereas the strong mineral acids do. Lower molecular mass organic acids such as formic and lactic acids are miscible in water, but higher molecular mass organic acids, such as benzoic acid, are insoluble in molecular (neutral) form.
On the other hand, most organic acids are very soluble in organic solvents. p-Toluenesulfonic acid is a comparatively strong acid used in organic chemistry often because it is able to dissolve in the organic reaction
Organometallic compounds are those compounds having bonds between an one or more metal atoms and one or more carbon atoms of an organyl group. They are classified by prefixing the metal with organo-, e.g. organopalladium compounds. In addition to the traditional metals and semimetals, elements such as boron, silicon, arsenic and selenium are considered to form organometallic compounds. Examples include organomagnesium compounds such as iodo(methyl)magnesium MeMgI, diethylmagnesium (EtMg); organolithium compounds such as butyllithium (BuLi), organozinc compounds such as chloro(ethoxycarbonylmethyl)zinc (ClZnCHC(=O)OEt); organocopper compounds such as lithium dimethylcuprate (Li[CuMe]); and organoborane compounds such as triethylborane (EtB).
The status of compounds in which the canonical anion has a delocalized structure in which the negative charge is shared with an atom more electronegative than carbon, as in enolates, may vary with the nature of the anionic moiety, the metal ion, and possibly the medium; in the absence ofdirect structural evidence for a carbon￢ﾀﾓmetal bond, such compounds are not considered to be organometallic.
Depending mostly on the nature of metallic ion
In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another the oxidant, also called the electron acceptor. This group of enzymes usually utilizes NADP or NAD+ as cofactors.
For example, an enzyme that catalyzed this reaction would be an oxidoreductase:
In this example, A is the reductant (electron donor) and B is the oxidant (electron acceptor).
In biochemical reactions, the redox reactions are sometimes more difficult to see, such as this reaction from glycolysis:
In this reaction, NAD is the oxidant (electron acceptor), and glyceraldehyde-3-phosphate is the reductant (electron donor).
Proper names of oxidoreductases are formed as "donor:acceptor oxidoreductase"; however, other names are much more common. The common name is "donor dehydrogenase" when possible, such as glyceraldehyde-3-phosphate dehydrogenase for the second reaction above. Common names are also sometimes formed as "acceptor reductase", such as NAD reductase. "Donor oxidase" is a special case where O2 is the acceptor.
Oxidoreductases are classified as EC 1 in the EC number classification of enzymes.
In organic chemistry, a polycyclic compound is a cyclic compound with more than one hydrocarbon loop or ring structures (benzene rings). In general, the term includes all polycyclic aromatic compounds, including the polycyclic aromatic hydrocarbons, the heterocyclic aromatic compounds containing sulfur, nitrogen, oxygen, or another non-carbon atoms, and substituted derivatives of these.
A heptose is a monosaccharide with seven carbon atoms.
They have either an aldehyde functional group in position 1 (aldoheptoses) or a ketone functional group in position 2 (ketoheptoses).
There are few examples of C-7 sugars in nature, among which are:
Ketoheptoses have 4 chiral centers, whereas aldoheptoses have 5.
An organic compound is any member of a large class of gaseous, liquid, or solid chemical compounds whose molecules contain carbon. For historical reasons discussed below, a few types of carbon-containing compounds such as carbides, carbonates, simple oxides of carbon (such as CO and CO2), and cyanides, as well as the allotropes of carbon such as diamond and graphite, are considered inorganic. The distinction between "organic" and "inorganic" carbon compounds, while "useful in organizing the vast subject of chemistry... is somewhat arbitrary".
Organic chemistry is the science concerned with all aspects of organic compounds. Organic synthesis is the methodology of their preparation.
The word "organic" is historical, dating back to the 1st century.(See Leviticus 11 and Romans 14:2) For many centuries, Western alchemists believed in vitalism. This is the theory that certain compounds could be synthesized only from their classical elements — Earth, Water, Air, and Fire — by action of a "life-force" (vis vitalis) possessed only by organisms. Vitalism taught that these "organic" compounds were fundamentally different from the "inorganic" compounds that could be obtained from the elements
A triose is a monosaccharide, or simple sugar, containing three carbon atoms. There are only three possible trioses: L-Glyceraldehyde and D-Glyceraldehyde, both aldotrioses because the carbonyl group is at the end of the chain, and dihydroxyacetone, a ketotriose because the carbonyl group is in the middle of the chain.
Trioses are important in cellular respiration. During glycolysis, Fructose-1,6-diphosphate is broken down into glyceraldehyde-3-phosphate and dihydroxyacetone phosphate. lactic acid and pyruvic acid are later derived from these molecules.
A glucan molecule is a polysaccharide of D-glucose monomers linked by glycosidic bonds.
Many beta-glucans are medically important.
The following are glucans: (The α- and β- and numbers clarify the type of O-glycosidic bond.)
Properties of Glucans include resistance to oral acids/enzyme and water insolubility.Glucans extracted from grains tend to be both soluble and insoluble.
A lactam (the noun is a portmanteau of the words lactone + amide) is a cyclic amide. Prefixes indicate how many carbon atoms (apart from the carbonyl moiety) are present in the ring: β-lactam (2 carbon atoms outside the carbonyl, 4 ring atoms in total), γ-lactam (3 and 5 total), δ-lactam (4 and 6 total). Beta β, gamma γ and delta δ are the second, third and fourth letters in the alphabetical order of the Greek alphabet, respectively.
General synthetic methods exist for the organic synthesis of lactams.
Lactim is a cyclic carboximidic acid compound characterized by an endocyclic carbon-nitrogen double bond. It is formed when lactam undergoes tautomerization.
Benzocycloheptenes are cycloheptenes with additional benzene rings attached. Most have two benzene rings, and are called "dibenzocycloheptenes".
Some benzocycloheptenes have medical uses as antihistamines or antidepressants.
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls. Aromatic hydrocarbons (arenes), alkanes, alkenes, cycloalkanes and alkyne-based compounds are different types of hydrocarbons.
The majority of hydrocarbons found naturally occur in crude oil, where decomposed organic matter provides an abundance of carbon and hydrogen which, when bonded, can catenate to form seemingly limitless chains.
The classifications for hydrocarbons defined by IUPAC nomenclature of organic chemistry are as follows:
Hydrocarbons can be gases (e.g. methane and propane), liquids (e.g. hexane and benzene), waxes or low melting solids (e.g. paraffin wax and naphthalene) or polymers (e.g. polyethylene, polypropylene and polystyrene).
Because of differences in molecular structure, the empirical formula remains different between hydrocarbons; in linear, or "straight-run" alkanes, alkenes and alkynes, the amount of bonded hydrogen lessens in alkenes and alkynes due to the "self-bonding" or catenation of carbon preventing entire saturation of the hydrocarbon by the
n−6 fatty acids (popularly referred to as ω−6 fatty acids or omega-6 fatty acids) are a family of unsaturated fatty acids that have in common a final carbon–carbon double bond in the n−6 position, that is, the sixth bond, counting from the methyl end.
The biological effects of the n−6 fatty acids are largely mediated by their conversion to n-6 eicosanoids that bind to diverse receptors found in every tissue of the body. The conversion of tissue arachidonic acid (20:4n-6) to n-6 prostaglandin and n-6 leukotriene hormones provides many targets for pharmaceutical drug development and treatment to diminish excessive n-6 actions in atherosclerosis, asthma, arthritis, vascular disease, thrombosis, immune-inflammatory processes, and tumor proliferation. Competitive interactions with the n−3 fatty acids affect the relative storage, mobilization, conversion and action of the n-3 and n-6 eicosanoid precursors. (See Essential fatty acid interactions for more information.)
Linoleic acid (18:2, n−6), the shortest-chained n−6 fatty acid, is an essential fatty acid. Arachidonic acid (20:4) is a physiologically significant n−6 fatty acid and is the precursor for prostaglandins and other
Cyclic peptides (or cyclic proteins) are polypeptide chains whose amino and carboxyl termini are themselves linked together with a peptide bond that forms a circular chain. A number of cyclic peptides have been discovered in nature and they can range anywhere from just a few amino acids in length, to hundreds. Cyclic peptides can be classified according to the types of bonds that comprise the ring. Homodetic cyclic peptides, such as cyclosporine A, are those in which the ring is composed exclusively of normal peptide bonds (i.e. between the alpha carboxyl of one residue to the alpha amine of another). Cyclic isopeptides contain at least one non-alpha amide linkage, such as a linkage between the side chain of one residue to the alpha carboxyl group of another residue, as in microcystin and bacitracin. Cyclic depsipeptides, such as aureobasidin A and HUN-7293, have at least one lactone (ester) linkage in place of one of the amides. Some cyclic depsipeptides are cyclized between the C-terminal carboxyl and the side chain of a Thr or Ser residue in the chain, such as kahalalide F, theonellapeptolide, and didemnin B. Bicyclic peptides such as the amatoxins amanitin and phalloidin
A mineral acid (or inorganic acid) is an acid derived from one or more inorganic compounds, and all mineral acids form hydrogen ions and the conjugate base ions when dissolved in water.
Commonly used mineral acids are sulfuric acid, hydrochloric acid and nitric acid (They are also known as bench acids). Mineral acids range from acids of great strength (example: sulfuric acid) to very weak (boric acid). Mineral acids tend to be very soluble in water and insoluble in organic solvents.
Mineral acids are used in many sectors of the chemical industry as feedstocks for the synthesis of other chemicals, both organic and inorganic. Large quantities of these acids, especially sulfuric acid, nitric acid and hydrochloric acid are manufactured for commercial use in large plants.
Mineral acids are also used directly for their corrosive properties. For example, a dilute solution of hydrochloric acid is used for removing the deposits from the inside of boilers, with precautions taken to prevent the corrosion of the boiler by the acid. This process is known as descaling.
Flavones (flavus = yellow), are a class of flavonoids based on the backbone of 2-phenylchromen-4-one (2-phenyl-1-benzopyran-4-one) shown on the right.
Natural flavones include Apigenin (4',5,7-trihydroxyflavone), Luteolin (3',4',5,7-tetrahydroxyflavone) and Tangeritin (4',5,6,7,8-pentamethoxyflavone), chrysin(5,7-OH), 6-hydroxyflavone, baicalein (5,6,7-trihydroxyflavone), scutellarein(5,6,7,4'-tetrahydroxyflavone), wogonin (5,7 -OH, 8 -OCH3). Synthetic flavones are Diosmin and Flavoxate.
The enzyme encoded by the gene UGT1A8 has glucuronidase activity with many substrates including flavones.
Flavones are mainly found in cereals and herbs. In the West, the estimated daily intake of flavones is in the range 20–50 mg per day. In recent years, scientific and public interest in flavones has grown enormously due to their putative beneficial effects against atherosclerosis, osteoporosis, diabetes mellitus and certain cancers. Flavones intake in the form of dietary supplements and plant extracts has been steadily increasing.
Natural dietary flavones, found in parsley, celery, and citrus peels, reactivate DLC1 (Deleted in Liver Cancer 1) expression in breast cancer cell lines which have
The bromate anion, BrO−
3, is a bromine-based oxoanion. A bromate is a chemical compound that contains this ion. Examples of bromates include sodium bromate, (NaBrO3), and potassium bromate, (KBrO3).
Bromates are formed many different ways in municipal drinking water. The most common is the reaction of ozone and bromide:
Electrochemical processes, such as electrolysis of brine without a membrane operating to form hypochlorite, will also produce bromate when bromide ion is present in the brine solution.
Photoactivation (sunlight exposure) will encourage liquid or gaseous chlorine to generate bromate in bromide-containing water.
In laboratories bromates can be synthesized by dissolving Br2 in a concentrated solution of potassium hydroxide (KOH). The following reactions will take place (via the intermediate creation of hypobromite):
Bromate in drinking water is undesirable because it is a suspected human carcinogen. Its presence in Coca Cola's Dasani bottled water forced a recall of that product in the UK.
Although few by-products are formed by ozonation, ozone reacts with bromide ions in water to produce bromate. Bromide can be found in sufficient concentrations in fresh water to
Globular proteins, or spheroproteins are one of the three main protein classes, comprising "globe"-like proteins that are more or less soluble in aqueous solutions (where they form colloidal solutions). This characteristic distinguishes them from fibrous proteins (the other class), which are practically insoluble.
The term globin can refer more specifically to proteins including the globin fold.
The term globular protein is quite old (dating probably from the 19th century) and is now somewhat archaic given the hundreds of thousands of proteins and more elegant and descriptive structural motif vocabulary. The globular nature of these proteins can be determined without the means of modern techniques, but only by using ultracentrifuges or dynamic light scattering techniques.
The spherical structure is induced by the protein's tertiary structure. The molecule's apolar (hydrophobic) amino acids are bounded towards the molecule's interior whereas polar (hydrophilic) amino acids are bound outwards, allowing dipole-dipole interactions with the solvent, which explains the molecule's solubility.
Globular protein is only marginally stable because the free energy released when the protein
The haloalkanes (also known as halogenoalkanes or alkyl halides) are a group of chemical compounds derived from alkanes containing one or more halogens. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely used commercially and, consequently, are known under many chemical and commercial names. They are used as flame retardants, fire extinguishants, refrigerants, propellants, solvents, and pharmaceuticals. Subsequent to the widespread use in commerce, many halocarbons have also been shown to be serious pollutants and toxins. For example, the chlorofluorocarbons have been shown to lead to ozone depletion. Methyl bromide is a controversial fumigant. Only haloalkanes which contain chlorine, bromine, and iodine are a threat to the ozone layer, but fluorinated volatile haloalkanes in theory may have activity as greenhouse gases. Methyl iodide, a naturally occurring substance, however, does not have ozone-depleting properties and the United States Environmental Protection Agency has designated the compound a non-ozone layer depleter. For more information, see Halomethane.
Haloalkanes have been known for centuries. Ethyl
A polyol is an alcohol containing multiple hydroxyl groups. In two technological disciplines the term "polyol" has a special meaning: food science and polymer chemistry.
Sugar alcohols, a class of polyols, are commonly added to foods because of their lower calorific content than sugars; however, they are also, in general, less sweet, and are often combined with high-intensity sweeteners. They are also added to chewing gum because they are not broken down by bacteria in the mouth or metabolized to acids, and thus do not contribute to tooth decay. Maltitol, sorbitol, xylitol and isomalt are some of the more common types. Sugar alcohols may be formed under mild reducing conditions from their analogue sugars.
In polymer chemistry, polyols are compounds with multiple hydroxyl functional groups available for organic reactions. A molecule with two hydroxyl groups is a diol, one with three is a triol, one with four is a tetrol and so on.
Monomeric polyols such as glycerin, pentaerythritol, ethylene glycol and sucrose often serve as the starting point for polymeric polyols. These materials are often referred to as the "initiators" and reacted with propylene oxide or ethylene oxide to
Proteins ( /ˈproʊˌtiːnz/ or /ˈproʊti.ɨnz/) are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function.
A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues. The sequence of amino acids in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 20 standard amino acids; however, in certain organisms the genetic code can include selenocysteine and—in certain archaea—pyrrolysine. Shortly after or even during synthesis, the residues in a protein are often chemically modified by posttranslational modification, which alters the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors. Proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes.
Like other biological macromolecules such as polysaccharides
Dicarboxylic acids are organic compounds that contain two carboxylic acid functional groups. In molecular formulae for dicarboxylic acids, these groups are often written as HOOC-R-COOH, where R may be an alkyl, alkenyl, alkynyl, or aryl group. Dicarboxylic acids can be used to prepare copolymers such as polyamides and polyesters.
In general, dicarboxylic acids show the same chemical behaviour and reactivity as monocarboxylic acids. The ionization of the second carboxyl group occurs less readily than the first one. This is because more energy is required to separate a positive hydrogen ion from the anion than from the neutral molecule.
A mnemonic to aid in remembering the order of the common nomenclature for the first six dicarboxylic acids is "Oh my, such great apple pie!" (oxalic, malonic, succinic, glutaric, adipic, pimelic). A variant adds "Sweet as sugar!" (suberic, azelaic, sebacic) to the end of the mnemonic. An additional way of remembering the first six dicarboxylic acids is by simply recalling the acronym OMSGAP, which is a simplification of the previously described mnemonic device.
When one of the carboxy groups is replaced with an aldehyde group, the resulting structure
A vitamin (US /ˈvaɪtəmɪn/ or UK /ˈvɪtəmɪn/) is an organic compound required by an organism as a vital nutrient in limited amounts. An organic chemical compound (or related set of compounds) is called a vitamin when it cannot be synthesized in sufficient quantities by an organism, and must be obtained from the diet. Thus, the term is conditional both on the circumstances and on the particular organism. For example, ascorbic acid (vitamin C) is a vitamin for humans, but not for most other animals, and biotin and vitamin D are required in the human diet only in certain circumstances. By convention, the term vitamin does not include other essential nutrients such as dietary minerals, essential fatty acids, or essential amino acids (which are needed in larger amounts than vitamins), nor does it encompass the large number of other nutrients that promote health but are otherwise required less often. Thirteen vitamins are universally recognized at present.
Vitamins are classified by their biological and chemical activity, not their structure. Thus, each "vitamin" refers to a number of vitamer compounds that all show the biological activity associated with a particular vitamin. Such a set
A group of weak acids with the general chemical formula RC(=O)N(R')OH and antineoplastic and antimicrobial activities. Hydroxamic acids covalently bind to the zinc(II) ion in the active sites of matrix metalloproteinases (MMP), thereby inhibiting the action of MMPs, inducing extracellular matrix degradation, and inhibiting angiogenesis, tumor growth and invasion, and metastasis. (NCI04)
Mycolic acids are long fatty acids found in the cell walls of the mycolata taxon, a group of bacteria that includes Mycobacterium tuberculosis, the causative agent of the disease tuberculosis. They form the major component of the cell wall of mycolata species. Despite their name, mycolic acids have no biological link to fungi; the name arises from the filamentous appearance their presence gives mycolata under high magnification. The presence of mycolic acids in the cell wall also gives mycolata a distinct gross morphological trait known as "cording." Mycolic acids were first isolated by Stodola et al. in 1938 from an extract of M. tuberculosis.
Mycolic acids are composed of a longer beta-hydroxy chain with a shorter alpha-alkyl side chain. Each molecule contains between 60 and 90 carbon atoms. The exact number of carbons varies by species and can be used as an identification aid. Most mycolic acids also contain various functional groups.
M. tuberculosis produces three main types of mycolic acids: alpha-, methoxy-, and keto-. Alpha-mycolic acids comprise at least 70% of the mycolic acids present in the organism and contain several cyclopropane rings. Methoxy-mycolic acids, which
A peroxy acid (often spelled as one word, peroxyacid, and sometimes called peracid) is an acid which contains an acidic -OOH group. The two main classes are those derived from conventional mineral acids, especially sulfuric acid, and the organic derivatives of carboxylic acids. They are generally strong oxidizers.
Peroxysulfuric acid (Caro's acid) is probably the most important inorganic peracid, at least in terms of the scale. It is used for the bleaching of pulp and for the detoxification of cyanide in the mining industry. It is produced by treating sulfuric acid with hydrogen peroxide. Peroxyphosphoric acid (H3PO5) is prepared similarly.
Several organic peroxyacids are commercially useful. They can be prepared in several ways. Most commonly, peracids are generated by treating the corresponding carboxylic acid with hydrogen peroxide:
A related reaction involves treatment of the carboxylic anhydride:
This method is popular for converting cyclic anhydrides to the corresponding monoperoxyacids, for example monoperoxyphthalic acid. The third method involves treatment of acid chlorides:
meta-chloroperoxybenzoic acid (mCPBA) is prepared in this way.
Peroxycarboxylic acids are about
In organic chemistry, a hexose is a monosaccharide with six carbon atoms, having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, and ketohexoses having a ketone at position 2.
The aldohexoses have four chiral centres for a total of 16 possible aldohexose stereoisomers (2). The D/L configuration is based on the orientation of the hydroxyl at position 5, and does not refer to the direction of optical activity. The eight D-aldohexoses are:
Of these D-isomers, all except D-altrose are naturally occurring. L-Altrose, however, has been isolated from strains of the bacterium Butyrivibrio fibrisolvens.
A mnemonic for the aldohexoses is "All Altruists Gladly Make Gum in Gallon Tanks": allose, altrose, glucose, mannose, gulose, idose, galactose, talose. When drawn in this order, the Fischer projections of the D-aldohexoses follow a pattern. Allose has all four hydroxyl groups on the right. At carbon 2, the hydroxyl groups alternate right-left. At carbon 3, the first two are on the right, the next two are on the left, and so on. At carbon 4, the first four are on the right and the rest are on the left. At carbon 5,
Oxazines are heterocyclic compounds containing one oxygen and one nitrogen.
Many isomers exist depending on the relative position of the heteroatoms and relative position of the double bonds
By extension, the derivatives are also referred to as oxazines; examples include ifosfamide and morpholine (tetrahydro-1,4-oxazine). A commercially available dihydro-1,3-oxazine is a reagent in the Meyers synthesis for aldehydes. Fluorescent dyes such as Nile red and Nile blue are based on the aromatic benzophenoxazine.
Benzoxazine is a molecule where an oxazine ring a heterocyclic six-membered ring with oxygen and nitrogen atom which is attached to a benzene ring. There are several benzoxazine structures depending on the position of the heteroatoms. The numbering is made in such a way that the oxygen position precedes the nitrogen. Thus, structure c is a 1,4-benzoxazine. This is because the benzoxazine was originally the compound with a double bond, such as in structured. The word, dihydro, indicates the hydrogenated version of benzoxazine. It is the 1,3-benzoxazines that are the subject of interest for development of polymeric materials as this class of benzoxazines readily polymerizes via
Proteinogenic amino acids are amino acids that are precursors to proteins, and are produced by cellular machinery coded for in the genetic code of any organism. There are 22 standard amino acids, but only 21 are found in eukaryotes. Of the 22, selenocysteine and pyrrolysine are incorporated into proteins by distinctive biosynthetic mechanisms. The other 20 are directly encoded by the universal genetic code. Humans can synthesize 11 of these 20 from each other or from other molecules of intermediary metabolism. The other 9 must be consumed (usually as their protein derivatives) in the diet and so are thus called essential amino acids. The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.
The word proteinogenic means "protein building". Proteinogenic amino acids can be condensed into a polypeptide (the subunit of a protein) through a process called translation (the second stage of protein biosynthesis, part of the overall process of gene expression).
In contrast, non-proteinogenic amino acids are either not incorporated in proteins (like GABA, L-DOPA, or triiodothyronine), or are not produced directly and
Triterpenoid saponins are triterpenes which belong to the group of saponin compounds. Triterpenes belong to a large group of compounds arranged in a four or five ring configuration of 30 carbons with several oxygens attached. Triterpenes are assembled from a C5 isoprene unit through the cytosolic mevalonate pathway to make a C30 compound and are steroidal in nature. Cholesterol is one example of a triterpene. Phytosterols and phytoecdysteroids are also triterpenes. The triterpenes are subdivided into some 20 groups, depending on their particular structures. Though all terpenoid compounds have bioactivity in mammals, it is the triterpenes that are most important to the adaptogenic effect found in plants such as Panax ginseng or Eleutherococcus senticosus. Most triterpenoid compounds in adaptogenic plants are found as saponin glycosides which refers to the attachment of various sugar molecules to the triterpene unit. These sugars can be easily cleaved off in the gut by bacteria, allowing the aglycone (triterpene) to be absorbed. This allows them insert into cell membranes and modify the composition, influence membrane fluidity, and potentially affect signaling by many ligands and
Amino acids ( /əˈmiːnoʊ/, /əˈmaɪnoʊ/, or /ˈæmɪnoʊ/) are biologically important molecules made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen. About 500 amino acids are known which can be classified in many ways. Structurally they can be classified according to the functional groups' locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, acid/base/neutral, and side chain group type (including: aliphatic, acyclic, hydroxyl or sulphur-containing, aromatic). In the form of proteins, amino acids comprise the second largest component other than water of human muscles, cells and other tissues. Outside proteins, amino acids also perform critical biological roles including neurotransmitters, transport, and in synthesis.
Amino acids having both the amine and carboxylic acid groups attached to the first, or alpha, carbon atom have particular importance in biochemistry. They are known as 2-, alpha-, or α-amino acids (generic formula H2NCHRCOOH in most cases where R is an organic
In chemistry an arsenite is a chemical compound containing an arsenic oxoanion where arsenic has oxidation state +3.
The different forms of the anion are the next ones:
Examples of arsenites include sodium arsenite which contains a polymeric linear anion, [AsO2]n, and silver arsenite, Ag3AsO3, which contains the trigonal, AsO3 anion.
Arsenite contrasts to the corresponding anions of the lighter members of group 15, phosphite which has the structure HPO3 and nitrite, NO2 which is bent. Sodium arsenite is used in the water gas shift reaction to remove carbon dioxide. Arsenites are salts of arsenious acid.
Note that in fields that commonly deal with groundwater chemistry, arsenite commonly refers to As2O3, the acid anhydride of arsenious acid. Its white odorless crystals are toxic and very soluble in water. It occurs in nature as arsenolite and claudetite, and is also a byproduct of metal smelting. Its main use is in producing chromated copper arsenate (CCA) to treat timber. It is also used for arsenic pesticides, glass production, pharmaceuticals and non-ferrous alloys.
Some species of bacteria obtain their energy by oxidizing various fuels while reducing arsenates to form arsenites.
Alkanes (also known as paraffins or saturated hydrocarbons) are chemical compounds that consist only of hydrogen and carbon atoms and are bonded exclusively by single bonds (i.e., they are saturated compounds) without any cycles (or loops; i.e., cyclic structure). With the formula CnH2n+2, Alkanes belong to a homologous series of organic compounds in which the members differ by a constant relative molecular mass of 14. They have two main commercial sources: crude oil and natural gas.
Each carbon atom has 4 bonds (either C-H or C-C bonds), and each hydrogen atom is joined to a carbon atom (H-C bonds). A series of linked carbon atoms is known as the carbon skeleton or carbon backbone. The number of carbon atoms is used to define the size of the alkane (e.g., C2-alkane).
An alkyl group, generally abbreviated with the symbol R, is a functional group or side-chain that, like an alkane, consists solely of single-bonded carbon and hydrogen atoms, for example a methyl or ethyl group.
The simplest possible alkane (the parent molecule) is methane, CH4. There is no limit to the number of carbon atoms that can be linked together, the only limitation being that the molecule is acyclic, is
The term carotene (also carotin, from the Latin carota, or carrot) is used for several related unsaturated hydrocarbon substances having the formula C40Hx, which are synthesized by plants but cannot be made by animals. Carotene is an orange photosynthetic pigment important for photosynthesis. Carotenes are all coloured to the human eye. They are responsible for the orange colour of the carrot, for which this class of chemicals is named, and for the colours of many other fruits and vegetables (for example, sweet potatoes and orange cantaloupe melon). Carotenes are also responsible for the orange (but not all of the yellow) colours in dry foliage. They also (in lower concentrations) impart the yellow colouration to milk-fat and butter. Omnivorous animal species which are relatively poor converters of coloured dietary carotenoids to colourless retinoids have yellowed-coloured body fat, as a result of the carotenoid retention from the vegetable portion of their diet. The typical yellow-coloured fat of humans and chickens is a result of fat storage of carotenes from their diets.
Carotenes contribute to photosynthesis by transmitting the light energy they absorb from chlorophyll. They
Crown ethers are cyclic chemical compounds that consist of a ring containing several ether groups. The most common crown ethers are oligomers of ethylene oxide, the repeating unit being ethyleneoxy, i.e., -CH2CH2O-. Important members of this series are the tetramer (n = 4), the pentamer (n = 5), and the hexamer (n = 6). The term "crown" refers to the resemblance between the structure of a crown ether bound to a cation, and a crown sitting on a person's head. The first number in a crown ether's name refers to the number of atoms in the cycle, and the second number refers to the number of those atoms that are oxygen. Crown ethers are much broader than the oligomers of ethylene oxide; an important group are derived from catechol.
Crown ethers strongly bind certain cations, forming complexes. The oxygen atoms are well situated to coordinate with a cation located at the interior of the ring, whereas the exterior of the ring is hydrophobic. The resulting cations often form salts that are soluble in nonpolar solvents, and for this reason crown ethers are useful in phase transfer catalysis. The denticity of the polyether influences the affinity of the crown ether for various cations. For
The ellagitannins are a diverse class of hydrolyzable tannins, a type of polyphenol formed primarily from the oxidative linkage of galloyl groups in 1,2,3,4,6-Pentagalloyl glucose. Ellagitannins differ from gallotannins, in that their galloyl groups are linked through C-C bonds, whereas the galloyl groups in gallotannins are linked by depside bonds.
Ellagitannins contain various numbers of hexahydroxydiphenoyl (HHDP) units, as well as galloyl units and/or sanguisorboyl units bounded to sugar moiety. In order to determine the quantity of every individual unit, the hydrolysis of the extracts with trifluoroacetic acid in methanol/water system is performed. Hexahydroxydiphenic acid, created after hydrolysis, spontaneously lactonized to ellagic acid, and sanguisorbic acid to sanguisorbic acid dilactone, while gallic acid remains intact.
Particular ellagitannins such as casuarictin have been shown to have potential antiviral activity.
The fruits of Rubus are a concentrated sources of dietary ellagitannins. The trimeric lambertianin C and the dimerics sanguiin H-6 are by far the major ellagitannins of Rubus berries. Lambertianin C is the major ellagitannin in blackberries and sanguiin H-6
Flavonols are a class of flavonoids that have the 3-hydroxyflavone backbone (IUPAC name : 3-hydroxy-2-phenylchromen-4-one). Their diversity stems from the different positions the phenolic -OH groups. They are distinct from flavanols (with an "a", like catechin), another class of flavonoids.
Flavonols are present in a wide variety of fruits and vegetables. In Western populations, estimated daily intake is in the range of 20–50 mg per day for flavonols. Individual intake varies depending on the type of diet consumed.
The phenomenon of dual fluorescence (due to excited state intramolecular proton transfer or ESIPT) is induced by tautomerism of flavonols (and glucosides) and could contribute to plant UV protection and flower colour.
Flavonoid have effects on CYP (P450) activity. Flavonols are inhibitor of CYP2C9 and CYP3A4, which are enzymes that metabolize most drugs in the body.
A heterocyclic compound is a cyclic compound that has atoms of at least two different elements as members of its ring(s). The counterparts of heterocyclic compounds are homocyclic compounds, the rings of which are made of a single element.
Although heterocyclic compounds may be inorganic, most contain at least one carbon. Since in organic chemistry non-carbons usually are considered to replace carbon atoms, they are called heteroatoms, meaning 'different from carbon and hydrogen' (rings of heteroatoms of the same element are homocyclic). The IUPAC recommends the Hantzsch-Widman nomenclature for naming heterocyclic compounds.
Heterocyclic chemistry is the branch of chemistry dealing with synthesis, properties, and applications of heterocycles.
Heterocyclic compounds can be usefully classified based on their electronic structure. The saturated heterocycles behave like the acyclic derivatives. Thus, piperidine and tetrahydrofuran are conventional amines and ethers, with modified steric profiles. Therefore, the study of heterocyclic chemistry focuses especially on unsaturated derivatives, and the preponderance of work and applications involves unstrained 5- and 6-membered rings.
Chemicals of this type:Delta-1-pyrroline-5-carboxylate
In chemistry, an imino acid is any molecule that contains both imino (>C=NH) and carboxyl (-C(=O)-OH) functional groups.
Imino acids are related to amino acids, which contain both amino (-NH2) and carboxyl (-COOH) functional groups, differing in the bonding to the nitrogen.
The amino acid oxidase enzymes are able to convert amino acids into imino acids. Also the direct biosynthetic precursor to the amino acid proline is the imino acid (S)-Δ-pyrroline-5-carboxylate (P5C).
Amino acids containing a secondary amine group (the only proteinogenic amino acid of this type is proline) are sometimes named imino acids, though this usage is disputed by some.
The term imino acid is also the obsolete term for imidic acids, containing the -C(=NH)-OH group, and should not be used for them.
Karyopherins are a group of proteins involved in transporting molecules between the cytoplasm and the nucleus of a eukaryotic cell. The inside of the nucleus is called the karyoplasm (or nucleoplasm). Generally, karyopherin-mediated transport occurs through the nuclear pore, which acts as a gateway into and out of the nucleus. Most proteins require karyopherins to traverse the nuclear pore.
Karyopherins can act as importins (i.e. help proteins get into the nucleus) or exportins (i.e. help proteins get out of the nucleus). They belong to 9.A.14 The Nuclear Pore Complex Family in the transporter classification database (TCDB).
Energy for transport is derived from the Ran gradient. See Ran for further details.
Importin beta is a karyopherin that facilitates transport of cargo proteins into the nucleus. First, it binds importin alpha, which is another karyopherin that binds the cargo protein in the cytoplasm. The cargo protein is imported into the nucleus through the nuclear pore using energy derived from the Ran gradient. Once inside the nucleus, the cargo dissociates from the karyopherins.
Importin beta can also carry proteins into the nucleus without the aid of the importin alpha
In chemistry, a ketone ( /ˈkiːtoʊn/) is an organic compound with the structure RC(=O)R', where R and R' can be a variety of carbon-containing substituents. It features a carbonyl group (C=O) bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology. Examples include many sugars and the industrial solvent acetone.
The word ketone derives its name from Aketon, an old German word for acetone.
According to the rules of IUPAC nomenclature, ketones are named by changing the suffix -ane of the parent alkane to -one. For the most important ketones, however, traditional nonsystematic names are still generally used, for example acetone and benzophenone. These nonsystematic names are considered retained IUPAC names, although some introductory chemistry textbooks use names such as 2-propanone or propan-2-one instead of acetone, the simplest ketone (CH3-CO-CH3). The position of the carbonyl group is usually denoted by a number.
Although used infrequently, "oxo" is the IUPAC nomenclature for a ketone functional group. Other prefixes, however, are also used. For some common chemicals (mainly in biochemistry), "keto" or "oxo" is the term
A phosphite is a salt of phosphorous acid. The phosphite ion (PO3) is a polyatomic ion with a phosphorus central atom where phosphorus has an oxidation state of +3. Its molecular geometry is trigonal pyramidal like ammonia.
Because phosphorous acid exists as an equilibrium tautomeric mixture of P(OH)3 and HP(O)(OH)2, predominantly the latter, there is some confusion in nomenclature. The IUPAC recommends that the trihydroxy form be called phosphorous acid and its salts phosphites, with the dihydroxy form being called phosphonic acid and its salts phosphonates, but despite this, salts of HP(O)(OH)2 are often called phosphites rather than phosphonates.
The term phosphite is also used to mean phosphite ester, an organophosphorus compound with the formula P(OR)3.
Acid or hydrogen phosphites (which the IUPAC recommends be called acid or hydrogen phosphonates), such as NH4HP(O)2OH, can be prepared from phosphorous acid, HP(O)(OH)2. Hydrogen bonding between anions leads to polymeric anionic structures. Recently some others, RbHPHO3, CsHPHO3, TlHPHO3 have been prepared by reacting phosphorous acid with the metal carbonate. These compounds contain a layer polymeric anion consisting of HPO3
Silicic acid is a general name for a family of chemical compounds containing the element silicon attached to oxide and hydroxyl groups. This family of compounds have the general formula [SiOx(OH)4-2x]n. Some simple silicic acids have been identified, but only in very dilute aqueous solution, such as metasilicic acid (H2SiO3), orthosilicic acid (H4SiO4, pKa1=9.84, pKa2=13.2 at 25 °C), disilicic acid (H2Si2O5), and pyrosilicic acid (H6Si2O7); however in the solid state these probably condense to form polymeric silicic acids of complex structure.
Silicic acids may be formed by acidification of silicate salts (such as sodium silicate) in aqueous solution. The main problem for the chemist is that these silicic acids readily lose water to form silica gel, a form of silicon dioxide. Such conversion involve condensations.
In the oceans, silicon exists primarily as orthosilicic acid (H4SiO4), and its biogeochemical cycle is regulated by the group of algae known as the diatoms. These algae polymerise the silicic acid to so-called biogenic silica, used to construct their cell walls (called frustules).
Continuing research of the correlation of aluminium and Alzheimer's disease has in the last
A tetrose is a monosaccharide with 4 carbon atoms. They have either an aldehyde functional group in position 1 (aldotetroses) or a ketone functional group in position 2 (ketotetroses).
The aldotetroses have two chiral centers ("asymmetric carbon atoms") and so 4 different stereoisomers are possible. There are two naturally occurring stereoisomers, the enantiomers of erythrose and threose having the D configuration but not the L enantiomers. The ketotetroses have one chiral center and, therefore, two possible stereoisomers: erythrulose (L- and D-form). Again, only the D enantiomer is naturally occurring.
Zein is a class of prolamine protein found in maize. It is usually manufactured as a powder from corn gluten meal.
Zein is one of the best understood plant proteins and has a variety of industrial and food uses. Historically, it has been used in the manufacture of a wide variety of commercial products, including coatings for paper cups, soda bottle cap linings, clothing fabric, buttons, adhesives, coatings and binders. The dominant historical use of zein was in the textile fibers market where it was produced under the name "Vicara". With the development of synthetic alternatives, the use of zein in this market eventually disappeared. By using electrospinning, zein fibers have again been produced in the lab, where additional research will be performed to re-enter the fiber market. Pure zein is clear, odorless, tasteless, hard, water-insoluble, and edible, making it invaluable in processed foods and pharmaceuticals, in competition with insect shellac. It is now used as a coating for candy, nuts, fruit, pills, and other encapsulated foods and drugs. In the United States, it may be labeled as "confectioner's glaze" (which may also refer to shellac-based glazes) and used as a coating on