Harrison Alex G
Department of Chemistry, University of Toronto, Ontario, Canada.
J Am Soc Mass Spectrom. 2002 Oct;13(10):1242-9. doi: 10.1016/S1044-0305(02)00455-5.
The fragmentation reactions of a variety of deprotonated dipeptides and tripeptides containing phenylalanine have been studied using energy-resolved collision-induced dissociation, isotopic labeling and MS/MS/MS experiments. The benzyl a-group has a substantial effect on the fragmentation reactions observed. When the phenylalanine is in the C-terminal position of dipeptides or tripeptides a major fragmentation reaction is elimination of neutral cinnamic acid to from a deprotonated amino acid amide (c1 ion) for dipeptides and a deprotonated dipeptide amide (c2 ion) for tripeptides. Fragmentation of the [M - H]- ions of tripeptides with phenylalanine in the central position also results in substantial formation of the deprotonated amide of the N-terminal amino acid residue. When the phenylalanine residue is in the N-terminal position elimination of C7H8 from the [M - H - CO2]- ion and formation of the benzyl anion become important fragmentation pathways. Sequence ions frequently observed are the y1 ions, "b2 ions and a3-Nt ions.
利用能量分辨碰撞诱导解离、同位素标记和串联质谱实验，研究了多种含苯丙氨酸的去质子化二肽和三肽的碎裂反应。苄基α-基团对观察到的碎裂反应有显著影响。当苯丙氨酸处于二肽或三肽的C端位置时，主要的碎裂反应是二肽脱去中性肉桂酸形成去质子化氨基酸酰胺（c1离子），三肽则形成去质子化二肽酰胺（c2离子）。苯丙氨酸处于中间位置的三肽的[M - H]-离子碎裂也会大量形成N端氨基酸残基的去质子化酰胺。当苯丙氨酸残基处于N端位置时，从[M - H - CO2]-离子中脱去C7H8并形成苄基阴离子成为重要的碎裂途径。经常观察到的序列离子有y1离子、b2离子和a3-Nt离子。
