ESI-MS studies of silver ion competitive interaction with cysteine-containing peptides and sulfur-containing amino aсids

Investigation of silver ion interaction with sulfur-containing amino acids and cysteine-containing peptides has been performed. Using an electrospray ionisation orthogonal ion introduction time-of-flight (ESI-O-TOF) mass spectrometer, it has been shown that Cys and Hcy exhibit the largest affinity for silver ions with respect to both methionine and cysteine residues in peptides. The effect of predominant formation of ions containing two silver atoms per a sulfhydryl group of cysteine-containing peptides, provided the nearest microenvironment does not hinder this, was revealed for the first time.