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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 ...
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.
The amino acid cysteine has a thiol functional group, consequently many cofactors in proteins and enzymes feature cysteinate-metal cofactors. [1] The zinc finger motif, which is found in transcription factors, is a metal thiolate complex. Structure of [Fe 4 S 4 (SMe) 4] 2−, a synthetic analogue of 4Fe-4S cofactors. [2]
Lewis structure of a water molecule. Lewis structures – also called Lewis dot formulas, Lewis dot structures, electron dot structures, or Lewis electron dot structures (LEDs) – are diagrams that show the bonding between atoms of a molecule, as well as the lone pairs of electrons that may exist in the molecule.
As the functional group of the amino acid cysteine, the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can generate a cystine unit with a disulfide bond (−S−S−).
A new report from the United States Department of Agriculture (USDA) suggests that beans and legumes are healthier proteins than lean meat: here's why.
Methionine (symbol Met or M) [3] (/ m ɪ ˈ θ aɪ ə n iː n /) [4] is an essential amino acid in humans.. As the precursor of other non-essential amino acids such as cysteine and taurine, versatile compounds such as SAM-e, and the important antioxidant glutathione, methionine plays a critical role in the metabolism and health of many species, including humans.
Selenocysteine has the same structure as cysteine, but with an atom of selenium taking the place of the usual sulfur. It has a selenol group. Like other natural proteinogenic amino acids, cysteine and selenocysteine have L chirality in the older D / L notation based on homology to D - and L-glyceraldehyde.