| disulphide bond | <chemistry, molecular biology> The S S linkage. A linkage formed between the SH groups of two cysteine moieties either within or between peptide chains. Each cysteine then becomes a half cystine residue. S S linkages stabilise, but do not determine, secondary structure in proteins. They are easily disrupted by SH groups in an exchange reaction and are not present in cytosolic proteins (cytosol has a high concentration of glutathione that has a free SH residue). (18 Nov 1997) |
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| double bond | <chemistry> A covalent bond resulting from the sharing of two pairs of electrons; e.g., H2C==CH2 (ethylene). (05 Mar 2000) |
| isopeptide bond | An amide linkage between a carboxyl group of one amino acid and an amino group of another amino acid in which at least one of these groups is not on the a-carbon of one of the amino acids; for example, the bond between the glutamyl residue and the cysteinyl residue of glutathione. Compare: peptide bond, eupeptide bond. (05 Mar 2000) |
| electrostatic bond | Bond between atoms or groups carrying opposite charges (or, in some cases, partial charges). Synonym: heteropolar bond, salt bridge. (05 Mar 2000) |
| energy-rich bond | See: high energy compounds. (05 Mar 2000) |
| triple bond | A covalent bond resulting from the sharing of three pairs of electrons; e.g., HC≡CH (acetylene). (05 Mar 2000) |
| eupeptide bond | A peptide bond between the alpha-carboxyl group of one amino acid and the alpha-amino group of another amino acid. Compare: peptide bond, isopeptide bond. (05 Mar 2000) |