ESI-MS Studies of Silver Ion Competitive Interaction with Cysteine-Containing Peptides and Sulfur-Containing Amino Acids

The paper deals with investigation of silver ion interaction with sulfur-bearing amino acids and cysteinebearing peptides using an electrospray ionisation orthogonal ion introduction time-of-flight (ESI-o-TOF) mass spectrometer. It has been shown that Cys and Hcy demonstrate the largest affinity for silver, both in relation to methionine and cysteine residues in peptides. The studies have for the first time revealed the effect of predominant forming of ions containing two silver atoms per a sulfhydryl group of cysteine-bearing peptides if the nearest microenvironment does not hinder this.