S-S exchange of cysteine-containing peptides in different methods of mass spectrometric analysis

1. Mass spectra of five cysteine-containing peptides and their mixtures were obtained by mass spectrometry methods under the conditions of electron impact, chemical ionization, field desorption bombardment by accelerated electrons and extraction of ions from solution under atmospheric pressure. 2. It was found that under ESIAP conditions, the cysteine-containing peptides do not undergo the S-S exchange observed in their investigation by other ionization methods.