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Pyomelanin
Pyomelanin is one of the five basic types of melanin. It is a polymer resulting from the oxidation and polymerization of homogentisic acid (HGA). This brownish pigment can be produced by microorganisms such as bacteria and fungi. It has several properties such as metal bonding, redox and electron shuttle, and protective roles such as anti-microbial activity or anti-oxidative stress. These properties are mainly used in cosmetics and pharmacology. Historical context Pyomelanin was first discovered in 1897 by a French cavalryman. This molecule was reported as a “pyocyanic bacillus” by Maxime Radais at the Faculty of Pharmacy in Paris. To cure a rare disease, the alkaptonuria (ALK) that appeared in 1902, researches led to rediscover the “pyocyanic bacillus”, that was then reevaluated and validated as pyomelanin. Synthesis Natural synthesis In opposition to other types of melanin, pyomelanin is a molecule synthesized in the human body in specific cases, by Microorgani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polymerization Of HGA
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many forms of polymerization and different systems exist to categorize them. In chemical compounds, polymerization can occur via a variety of reaction mechanisms that vary in complexity due to the functional groups present in the reactants and their inherent steric effects. In more straightforward polymerizations, alkenes form polymers through relatively simple radical reactions; in contrast, reactions involving substitution at a carbonyl group require more complex synthesis due to the way in which reactants polymerize. As alkenes can polymerize in somewhat straightforward radical reactions, they form useful compounds such as polyethylene and polyvinyl chloride (PVC), which are produced in high tonnages each year due to their usefulness in manu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tyrosine
-Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is from the Greek ''tyrós'', meaning ''cheese'', as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic than phenylalanine. It is encoded by the codons UAC and UAU in messenger RNA. The one-letter symbol Y was assigned to tyrosine for being alphabetically nearest of those letters available. Note that T was assigned to the structurally simpler threonine, U was avoided for its similarity with V for valine, W was assigned to tryptophan, while X was reserved for undetermined or atypical amino acids. The mnemonic t''Y''rosine was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artificial Synthesis Pyoenz
Artificiality (the state of being artificial, anthropogenic, or man-made) is the state of being the product of intentional human manufacture, rather than occurring naturally through processes not involving or requiring human activity. Connotations Artificiality often carries with it the implication of being false, counterfeit, or deceptive. The philosopher Aristotle wrote in his ''Rhetoric'': However, artificiality does not necessarily have a negative connotation, as it may also reflect the ability of humans to replicate forms or functions arising in nature, as with an artificial heart or artificial intelligence. Political scientist and artificial intelligence expert Herbert A. Simon observes that "some artificial things are imitations of things in nature, and the imitation may use either the same basic materials as those in the natural object or quite different materials.Herbert A. Simon, ''The Sciences of the Artificial'' (1996), p. 4. Simon distinguishes between the artific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Decarboxylation
Decarboxylation is a chemical reaction that removes a carboxyl group and releases carbon dioxide (CO2). Usually, decarboxylation refers to a reaction of carboxylic acids, removing a carbon atom from a carbon chain. The reverse process, which is the first chemical step in photosynthesis, is called carboxylation, the addition of CO2 to a compound. Enzymes that catalyze decarboxylations are called decarboxylases or, the more formal term, carboxy-lyases (Enzyme Commission number, EC number 4.1.1). In organic chemistry The term "decarboxylation" usually means replacement of a carboxyl group () with a hydrogen atom: : Decarboxylation is one of the oldest known organic reactions. It is one of the processes assumed to accompany pyrolysis and destructive distillation. Overall, decarboxylation depends upon stability of the carbanion synthon , although the anion may not be a true chemical intermediate. Typically, carboxylic acids decarboxylate slowly, but carboxylic acids with an α el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Artificial Synthesis Pyochem
Artificiality (the state of being artificial, anthropogenic, or man-made) is the state of being the product of intentional human manufacture, rather than occurring naturally through processes not involving or requiring human activity. Connotations Artificiality often carries with it the implication of being false, counterfeit, or deceptive. The philosopher Aristotle wrote in his ''Rhetoric'': However, artificiality does not necessarily have a negative connotation, as it may also reflect the ability of humans to replicate forms or functions arising in nature, as with an artificial heart or artificial intelligence. Political scientist and artificial intelligence expert Herbert A. Simon observes that "some artificial things are imitations of things in nature, and the imitation may use either the same basic materials as those in the natural object or quite different materials.Herbert A. Simon, ''The Sciences of the Artificial'' (1996), p. 4. Simon distinguishes between the artific ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benzoquinone Acetic Acid
Benzoquinone (C6H4O2) is a quinone with a single benzene ring. There are 2 (out of 3 hypothetical) benzoquinones: * 1,4-Benzoquinone, most commonly, right image (also ''para''-benzoquinone, ''p''-benzoquinone, ''para''-quinone, or just quinone) * 1,2-Benzoquinone, less commonly, left image (also ''ortho''-benzoquinone, ''o''-benzoquinone, ''ortho''-quinone) *1,3-benzoquinone "does not exist, because its structure would be nonplanar and highly strained", though derivatives are known. An alkylated ''p''-benzoquinone has been found in the rhizomes of ''Iris kemaonensis''. See also * Arene substitution pattern Arene substitution patterns are part of organic chemistry IUPAC nomenclature and pinpoint the position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon. ''Ortho'', ''meta'', and ''para'' substitution * ... References {{Chemistry index ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manganese(II) Hydroxide
Manganese(II) hydroxide is the inorganic compound with the formula Mn (OH)2. It is a white solid although samples darken quickly upon exposure to air owing to oxidation. It is poorly soluble in water. Structure, preparation, and reactions Mn(OH)2 adopts the brucite structure, i.e. the arrangement of the atoms in the crystal are the same as the arrangement of the atoms in Mg(OH)2. The Mn(II) centers are bonded to six hydroxide ligands. Each hydroxide ligand bridges to three Mn(II) sites. The O-H bonds are perpendicular to the planes defined by the oxygen atoms, projecting above and below these layers. Manganese(II) hydroxide precipitates as a solid when an alkali metal hydroxide is added to an aqueous solution of Mn2+ salt:H. Lux "Manganese(IV) Hydroxide" in Handbook of Preparative Inorganic Chemistry, 2nd Ed. Edited by G. Brauer, Academic Press, 1963, NY. Vol. 1. p. 1456. :Mn2+ + 2 NaOH → Mn(OH)2 + 2 Na+ Manganese(II) hydroxide oxidises readily in air, as indicated ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Medroxyprogesterone Acetate
Medroxyprogesterone acetate (MPA), also known as depot medroxyprogesterone acetate (DMPA) in injectable form and sold under the brand name Depo-Provera among others, is a hormonal medication of the progestin type. It is used as a method of birth control and as a part of menopausal hormone therapy. It is also used to treat endometriosis, abnormal uterine bleeding, paraphilia, and certain types of cancer. The medication is available both alone and in combination with an estrogen. It is taken by mouth, used under the tongue, or by injection into a muscle or fat. Common side effects include menstrual disturbances such as absence of periods, abdominal pain, and headaches. More serious side effects include bone loss, blood clots, allergic reactions, and liver problems. Use is not recommended during pregnancy as it may harm the baby. MPA is an artificial progestogen, and as such activates the progesterone receptor, the biological target of progesterone. It also has androg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tyrosine
-Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is from the Greek ''tyrós'', meaning ''cheese'', as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic than phenylalanine. It is encoded by the codons UAC and UAU in messenger RNA. The one-letter symbol Y was assigned to tyrosine for being alphabetically nearest of those letters available. Note that T was assigned to the structurally simpler threonine, U was avoided for its similarity with V for valine, W was assigned to tryptophan, while X was reserved for undetermined or atypical amino acids. The mnemonic t''Y''rosine was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homogentisate 1,2-dioxygenase
Homogentisate 1,2-dioxygenase (homogentisic acid oxidase, homogentisate oxidase, homogentisicase) is an enzyme which catalyzes the conversion of homogentisate to 4-maleylacetoacetate. Homogentisate 1,2-dioxygenase or HGD is involved in the catabolism of aromatic rings, more specifically in the breakdown of the amino acids tyrosine and phenylalanine. HGD appears in the metabolic pathway of tyrosine and phenylalanine degradation once the molecule homogentisate is produced. Homogentisate reacts with HGD to produce maleylacetoacetate, which then is further used in the metabolic pathway. HGD requires the use of Fe2+ and O2 in order to cleave the aromatic ring of homogentisate. Image:Homogentisic acid.svg, homogentisate Image:4-maleylacetoacetic acid.svg, 4-maleylacetoacetate Enzyme active site The active site of Homogentisate 1,2-dioxygenase was determined through the crystal structure, which was captured through the work of Titus et al. Through the crystal structure the active ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
