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Cysteine (/ ˈ s ɪ s t ɪ iː n /; [5] symbol Cys or C [6]) is a semiessential [7] proteinogenic amino acid with the formula HOOC−CH(−NH 2)−CH 2 −SH. The thiol side chain in cysteine enables the formation of disulfide bonds, and often participates in enzymatic reactions as a nucleophile. Cysteine is chiral, but both D and L-cysteine ...
It has also been used for the laboratory diagnosis of Acanthamoeba keratitis, [2] Francisella and Nocardia spp. It contains L-cysteine amino acid and ferric pyrophosphate that assist in the growth of Legionnaire's species. The charcoal within the medium acts as a detoxicant because it decomposes hydrogen peroxide which is toxic to the legionellae.
Cystine tryptic agar (CTA), also known as cystine trypticase agar, [1] [2] is a growth medium used for the identification of microorganisms. [3]It can be used to determine if organisms can ferment various carbohydrates, including maltose, lactose, and sucrose.
Cystine is the oxidized derivative of the amino acid cysteine and has the formula (SCH 2 CH(NH 2)CO 2 H) 2.It is a white solid that is poorly soluble in water. As a residue in proteins, cystine serves two functions: a site of redox reactions and a mechanical linkage that allows proteins to retain their three-dimensional structure.
A clear CLED agar plate after cultivation Colonies of lactose and non-lactose fermenting bacteria on CLED agar. CLED agar (cystine–lactose–electrolyte-deficient agar or medium) is a valuable non-inhibitory growth medium used in the isolation and differentiation of urinary microbes.
It is a homologue of the amino acid cysteine, differing by an additional methylene bridge (-CH 2-). It is biosynthesized from methionine by the removal of its terminal C ε methyl group. In the body, homocysteine can be recycled into methionine or converted into cysteine with the aid of vitamin B 6, B 9, and B 12. [3]
The laboratory analysis of homocysteine itself is complicated because most homocysteine (possibly above 85%) is bound to other thiol amino acids and proteins in the form of disulphides (e.g., cysteine in cystine-homocysteine, homocysteine in homocysteine-homocysteine) via disulfide bonds. Since as an equilibrium process the proportion of free ...
The characteristic color of a positive biuret test. In chemistry, the biuret test (IPA: / ˌ b aɪ j ə ˈ r ɛ t /, / ˈ b aɪ j ə ˌ r ɛ t / [1]), also known as Piotrowski's test, is a chemical test used for detecting the presence of at least two peptide bonds in a molecule.