الرئيسية » Simplified Chemistry (صفحه 12)

Simplified Chemistry

actin

actin a major protein constituent of the thin filaments of muscle and of the microfilaments found in practically all eukaryotic cells – it comprises 5–10% of the protein of such cells (see actin filament). In solutions of low ionic strength, actin is a globular 42 kDa monomer, termed G-actin. At …

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acridinium esters

acridinium esters: esters of acridine-9-carboxylic acid. They have a quaternary nitrogen centre and are derivatized at the 9 position to give a labile phenyl ester moiety. Acridinium esters such as 2′,6′-dimethyl-4′-[N-succinimidyloxy carbonyl]phenyl-10-methylacridinium- 9-carboxylate can be used as chemiluminescent labels for antibodies. Light emission is activated by adding hydrogen peroxide under …

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الأكريدين البرتقالي Acridine Orange

صبغ يتميز بالألفة تجاه الحموض النووية. فمعقد الحمض النووي مع الصبغ يشع اللون البرتقالي عند ارتباطه ب RNA و بالأخضر مع DNA و ذلك عند رؤيته بالمجهر الفلورنسي . الصيغة الكيميائية لهذه المادة C17H19N3 و وزنها الجزيئي 265.35 .

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acridine

acridine the parent compound of a series of derivatives, e.g. 3,6-diaminoacridine (proflavin), that are potent mutagens. Some acridines are found in coal tar. They induce frameshift mutations during the replication of DNA by binding to DNA and distorting the double helix, causing additional bases to be incorporated or bases to …

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ackee

ackee or akee a tree, Blighia sapida, native to tropical Africa and widely cultivated in the West Indies, especially Jamaica, for its fruit, the fleshy aril of which is edible when cooked and forms an important item of local diet. Unripe fruits contain toxic amounts of hypoglycin and can cause …

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acid phosphatase

acid phosphatase , systematic name: orthophosphoric monoester phosphohydrolase (acid optimum); other names: alkaline phosphomonoesterase; phosphomonoesterase; glycerophosphatase; a lysosomal enzyme (except in red cells). It catalyses the hydrolysis of orthophosphoric monoester to an alcohol and orthophosphate. Zinc and magnesium are cofactors. It is present in high concentrations in the prostate gland, …

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acid dissociation constant

acid dissociation constant or acidity constant symbol: Ka; the thermodynamic equilibrium constant for the dissociation of an acid. For a dilute solution of a weak acid, HA, dissociating in water according to the equilibrium: HA + H2O  ↔ H3O+ + A–, Ka = (aH3O+ × aA–)/aHA where a is the …

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acid ceramidase

acid ceramidase , other name: N-acylsphingosine deacylase; a lysosomal enzyme that catalyses the hydrolyis of ceramide to sphingosine and a fatty acid. Its activity requires sphingolipid activator proteins (i.e. saposins B and C) and negatively charged phospholipids. A genetic locus at 8p21.3-22 encodes a precursor that contains 395 amino acids …

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acetyl coenzyme

acetyl coenzyme A or acetyl-CoA; a derivative of coenzyme A in which the sulfhydryl group is acetylated. Originally termed ‘active acetate’, it is an important metabolite, derived from pathways such as glycolysis, fatty-acid oxidation, and degradative metabolism of some amino acids. It is further metabolized by the tricarboxylic- acid cycle …

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acetylcholinesterase

acetylcholinesterase ,systematic name: acetylcholine acetylhydrolase; other names: true cholinesterase; cholinesterase I; an esterase enzyme that catalyses the hydrolysis of acetylcholine to choline and acetate; it also acts on a variety of acetic esters and catalyses transacetylations. It is found in or attached to cellular or basement membranes of presynaptic cholinergic …

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