Schwartz B L, Bursey M M
Department of Chemistry, University of North Carolina, Chapel Hill 27599-3290.
Biol Mass Spectrom. 1992 Feb;21(2):92-6. doi: 10.1002/bms.1200210206.
Tandem mass spectral effects of the replacement of alanine by proline in pentaalanine were studied. The principal difference when residue 3 or 4 is proline is the great enhancement of the y3 or y2 ion, respectively. This is precisely the principal difference which thermochemical arguments predict, since a y-type ion with N-terminal proline is estimated to be 32 kJ mol-1 more stable than with N-terminal alanine. When this proline effect and the effect of neutral diketopiperazine loss occur simultaneously, the y-type ion is not observed, as predicted from the additivity of substituent effects by the kinetic approach. No interpretation is offered for observations of b-type ion intensities, since the pattern is not obvious to us.
研究了在五聚丙氨酸中脯氨酸取代丙氨酸的串联质谱效应。当第3或第4位残基为脯氨酸时，主要差异分别是y3或y2离子的大幅增强。这正是热化学论据所预测的主要差异，因为据估计，N端为脯氨酸的y型离子比N端为丙氨酸的y型离子稳定32 kJ/mol。当这种脯氨酸效应和中性二酮哌嗪损失效应同时发生时，正如动力学方法根据取代基效应的加和性所预测的那样，未观察到y型离子。对于b型离子强度的观察结果未作解释，因为其模式对我们来说并不明显。
