ABSTRACT
The presence of intrachain disulfide bridges in peptides and proteins is a common feature. Examples of these bridges are found in peptide hormones such as insulin and vasopressin, in enzymes such as lysozyme, ribonuclease, and serine proteases and in small protease inhibitors such as trypsin inhibitors and kallikrein inactivators. The main function of these disulfide bridges is to stabilize the protein conformation. Reversed-phase high-performance liquid chromatography could be utilized as such a method if baseline separation between the reduced and oxidized conformers of the peptide could be achieved using standard conditions of chromatography. The main problem encountered in the formation of the intrachain disulfide bridge is the availability of a rapid and simple monitoring method to follow the extent of oxidation of the cysteine residues to cystine. In addition, a sensitive and quantitative method is required to resolve the disulfide bridged (oxidized) peptide from the corresponding cysteine containing (reduced) peptide.
