Lecchi Paolo, Olson Matthew, Brancia Francesco L
Department of Pharmacology and Physiology, George Washington University School of Medicine and Health Sciences, Washington, District of Columbia, USA.
J Am Soc Mass Spectrom. 2005 Aug;16(8):1269-74. doi: 10.1016/j.jasms.2005.03.019.
Esterification was used to investigate how introduction of aliphatic chains within the peptide structure affects the MALDI response of ions analyzed in both polarity regimes. In binary mixtures containing equimolar amounts of a peptide with its correspondent alkyl ester, derivatization of the carboxylic groups has the tendency to increase MALDI detection of the modified protonated peptide ions. This positive effect on ion yield is more pronounced when longer alcohols are employed. In negative mode, the situation is antithetic and esterification produces a deleterious effect on the ion yield of the corresponding deprotonated species. From the data reported here we postulate that modifications of the acidic character of peptides prevent formation of anionic species under MALDI analysis. Furthermore, suppression of the formation pathway for anions alters the overall number of molecules which can undergo protonation. This results in an increased ion yield for the protonated esters.
酯化反应被用于研究在肽结构中引入脂肪族链如何影响在两种极性模式下分析的离子的基质辅助激光解吸电离（MALDI）响应。在含有等摩尔量的肽及其相应烷基酯的二元混合物中，羧基的衍生化倾向于增加修饰的质子化肽离子的MALDI检测。当使用更长链的醇时，这种对离子产率的积极影响更为明显。在负模式下，情况相反，酯化反应会对相应去质子化物种的离子产率产生有害影响。根据此处报告的数据，我们推测肽酸性特征的改变会阻止在MALDI分析下形成阴离子物种。此外，阴离子形成途径的抑制改变了可进行质子化的分子总数。这导致质子化酯的离子产率增加。
