Concurrent mass spectrometric analysis of multiple samples using Py-Tag reagents

Abstract

The quantification of amino acids, peptides and proteins are important in fundamental science to understand intravital event, as well as in applied fields such as biological, medical, and pharmaceutical sciences.Py-Tags (Py0, Py6 and Py12) are primary amine-reactive isotope-labelled tagging reagents. Py-Tags can selectively and efficiently react with the primary amino group which has more than a two-carbon chain from the alpha-carbon of the target sample by the reaction of pyrylium salts with nucleophiles under alkaline conditions, thereby increasing the mass by 175.15, 181.17, and 187.19 Da, respectively, and generating positive ions.We used Py-Tags to label not only the amino acids but also peptides with a lysine residue(s), fragment peptides with a lysine(s), digested proteins, and intact proteins. All Py-Tag-labelled peptide sets showed similar mass differences. Thus, we could easily analyze expression ratio by single measurement. Furthermore, the ratio of the measured ion intensities was representative of the relative amount of each material.