GAS-PHASE FRAGMENTATION MECHANISMS STUDIES OF DOUBLY-PROTONATED PEPTIDE IONS CONTAINING BASIC AMINO ACID RESIDUES BY MASS SPECTROMETRY

摘要

In recent years, many studies have been carried out for the gas-phase reaction mechanisms of the protonated peptides using mass spectrometry and many of these studies are related with singly-protonated peptides (1). However, there are a few studies related to multiply- protonated peptides in the literature (2,3). Most of these studies are not systematic studies, therefore they are not sufficient enough to better understand the gas-phase reaction mechanisms of peptides. Multiply-protonated peptides can be generated in ESI-MS studies if the peptides contain a basic amino acid residues. In order to determine the amino acid sequence of the peptides correctly and reliable, the gas-phase reaction mechanism of peptides should be studied and understood very well. Multiply-protonated peptides can be easily formed if the peptide sequence consists of basic amino acid residue. As all know, when the proteins undergo enzymatic cleavage (especially with Trypsin), the C-terminal of truncated peptides always contain a basic amino acids such as lysine (K) or arginine (R). Especially, the gas-phase fragmentation mechanisms of multiply-protonated peptides should be investigated in details by MS to elucidate the sequence as well as the function of proteins.