Disulfide bond decay during matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry experiments

Abstract

In our laboratory, we have been studying the reductive processes that occur during matrix-assisted laser desorption/ionization (MALDI) experiments. Recently, we have finished an analysis of the DHB matrix effect on the azo group in cyclic peptides. However, deep understanding of disulfide bond behaviour during a mass spectrometry (MS) experiment is much more important in proteomics as its reduction can cause serious errors in protein spectra interpretation. Therefore, we have focused on intra- and intermolecular disulfide bonds as well as disulfide bonds connecting cysteine and 2-thio-5-nitrobenzoic acid (TNB, Ellman's reagent modification) in model peptides during MALDI MS measurements. While the reduction was not observed for intra- and intermolecular cysteine-cysteine disulfide bonds, the disulfide connection between cysteine and TNB was always affected. It was proved that TNB and Ellman's reagent can act as a matrix itself. The results obtained enabled us to propose a reaction mechanism model which is able to describe the phenomena observed during the desorption/ionization process of disulfide-containing molecules.

Mass spectral and theoretical investigations of N–Cαbond cleavages in the disulfide‐containing peptide TTCPYCKK and its analogues

“…All the octapeptides used in this work are listed in Table 1. Oxidized disulfide-containing forms were obtained by oxidations of the dithiol peptides, [24][25][26][27][28] and were investigated accordingly. We herein report the results obtained.…”