disulfide bond

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bond

 [bond]
the linkage between atoms or radicals of a chemical compound, or the symbol representing this linkage and indicating the number and attachment of the valencies of an atom in constitutional formulas, represented by a pair of dots or a line between atoms, e.g., H—O—H, H—C≡C—H or H:O:H, H:C:::C:H.
coordinate covalent bond a covalent bond in which one of the bonded atoms furnishes both of the shared electrons.
covalent bond a chemical bond between two atoms or radicals formed by the sharing of a pair (single bond), two pairs (double bond), or three pairs of electrons (triple bond).
disulfide bond a strong covalent bond, —S—S—, important in linking polypeptide chains in proteins, the linkage arising as a result of the oxidation of the sulfhydryl (SH) groups of two molecules of cysteine.
high-energy phosphate bond an energy-rich phosphate linkage present in adenosine triphosphate (ATP), phosphocreatine, and certain other biological molecules. On hydrolysis at pH 7 it yields about 8000 calories per mole, in contrast to the 3000 calories yielded by phosphate esters. The bond stores energy that is used to drive biochemical processes, such as the synthesis of macromolecules, contraction of muscles, and the production of the electrical potentials for nerve conduction.
high-energy sulfur bond an energy-rich sulfur linkage, the most important of which occurs in the acetyl-CoA molecule, the main source of energy in fatty acid biosynthesis.
hydrogen bond a weak, primarily electrostatic, bond between a hydrogen atom bound to a highly electronegative element (such as oxygen or nitrogen) in a given molecule, or part of a molecule, and a second highly electronegative atom in another molecule or in a different part of the same molecule.
ionic bond a chemical bond in which electrons are transferred from one atom to another so that one bears a positive and the other a negative charge, the attraction between these opposite charges forming the bond.
peptide bond the —CO—NH— linkage formed between the carboxyl group of one amino acid and the amino group of another; it is an amide linkage joining amino acids to form peptides.

di·sul·fide bond

a single bond between two sulfurs; specifically, the -S-S- link binding two peptide chains (or different parts of one peptide chain); also occurs as part of the molecule of the amino acid, cystine, and is important as a structural determinant in many peptide and protein molecules, for example, keratin, insulin, and oxytocin. A symmetric disulfide is R-S-S-R; R'-S-S-R is a mixed or asymmetric disulfide.

di·sul·fide bond

(dī-sŭl'fīd bond)
A single bond between two sulfurs; specifically, the -S-S- link binding two peptide chains (or different parts of one peptide chain).
Synonym(s): disulphide bond.
References in periodicals archive ?
(47) It was also hypothesized that a disulphide bond between Cys553 and Cys558 is cleaved by reducing agents such as dithiothreitol or that the antioxidant thioredoxin applied from the extracellular side induces opening of the TRPC5 channel.
Disulphide bonds can prevent partially the unfolding process and form links between protein molecules.
Human t-PA is a 70kd serine protease that contains 17 disulphide bonds which when secreted by both human and as a recombinant glycoprotein show variable sequon occupancy (38).
When in the same environment with ROS, - SH groups are oxidised and form reversible disulphide bonds. But formed disulphide bonds may again be reduced to thiol groups by the cellular-reducing effects of some anti-oxidants, and thiol-disulphide homeostasis is kept by this mechanism.
Histochemical examination of hair has shown that in the trichilemmal sac encircling hair the germinal cells rich in free thiol groups are abundant, and disulphide bonds limit themselves (24).
The number of disulphide bonds is given by half the value of the difference between total and native thiols.
For that purpose, the content of free sulphydryl groups (SH), disulphide bonds (SS), and free amino groups (N[H.sub.2]) as indicators of gluten quality was determined.
[11] The plasma thiol pool is mainly formed by albumin and protein thiols and slightly formed by low molecular weight thiols.12 Thiols can undergo oxidation reaction via oxidants and form disulphide bonds. The formed disulphide bonds can again be reduced to thiol groups; thus, dynamic thiol/disulphide homeostasis is maintained.
Various types of bonds are used in these links: hydrogen bonds between R groups, disulphide bonds between two cysteines molecules, as in the primary structure, ionic bonds between R groups containing amine and carboxyl groups, and hydrophobic reactions between R groups which are non-polar all contribute to holding the tertiary structure of a protein.
This result indicated that this enzyme could not completely cleave the disulphide bonds. Pretreatment of these substrates such as chicken feather, nail and human hair by physical method or reducing agents, or detergents, or activation of the enzyme by adding metal salts are required for the improvement of their degradation (Suntornsuk et al, 2005).
The [alpha]-keratin dimer is stabilized by hydrogen bonds as well as inter- and intramolecular disulphide bonds which are responsible for a compact three-dimensional stable structure [9,10].
The product (Lipoic Acid Choline Ester, 1.5%) is a first-in-class new chemical entity that targets a biochemical cause of presbyopia, believed to be associated with an increase in the formation of disulphide bonds between the crystalline proteins within lens fibre cells.