 A disulfide bond is typically denoted by hyphenating the abbreviations for cysteine, e.g., when referring to ribonuclease A the "Cys26–Cys84 disulfide bond", or the "26–84 disulfide bond", or most simply as "C26–C84" where the disulfide bond is understood and does not need to be mentioned.The prototype of a protein disulfide bond is the two-amino-acid peptide cystine, which is composed of two cysteine amino acids joined by a disulfide bond.The structure of a disulfide bond can be described by its "χ"ss dihedral angle between the Cβ−Sγ−Sγ−Cβ atoms, which is usually close to ±90°.