THE INFLUENCE OF STRONGLY ACIDIC GROUPS ON THE PROTONATION OF PEPTIDES IN ELECTROSPRAY MS

In order to obtain experimental data on the question of compensation o f positive charges by anionic groups in multiply charged ions of polyf unctional molecules in electrospray MS, several pairs of peptides with the same basic structure but differentiated by one or two strongly ac idic groups (phosphate or sulfonate) were investigated, It was found t hat depending on the density of basic centers and the strength of acid ic groups present, the observed changes upon introduction of acidic gr oups ranged from complete elimination of the most highly charged state to absence of any difference. (C) 1997 by John Wiley & Sons, Ltd. No. of Figures: 10 No. of Tables: 1 No. of Refs: 15.