Ionisation bias undermines the use of matrix‐assisted laser desorption/ionisation for estimating peptide deamidation: Synthetic peptide studies demonstrate electrospray ionisation gives more reliable response ratios

摘要

RationaleAlthough mass spectrometry (MS) is routinely used to determine deamination in peptide mixtures, the effects of the choice of ionisation source have not yet been investigated. In particular, matrix‐assisted laser desorption/ionisation (MALDI) has become a popular tool with which to measure levels of glutamine deamidation in ancient proteins. Here we use model synthetic peptides to rigorously compare MALDI and electrospray ionisation (ESI).