Brinkworth C S, Dua S, McAnoy A M, Bowie J H
Department of Chemistry, The University of Adelaide, South Australia 5005, Australia.
Rapid Commun Mass Spectrom. 2001;15(20):1965-73. doi: 10.1002/rcm.457.
The collision-induced spectra of M - H ions of a variety of natural and synthetic amphibian peptides containing Asp and/or Glu exhibit characteristic gamma backbone cleavage ions that identify the positions of these residues in the peptide. A theoretical study suggests that the Glu cleavage involves an S(N)i reaction of the carboxylate anion from the Glu alpha side chain to form a deprotonated cyclic lactone. The presence of either Asp or Glu or other residues that effect pronounced side-chain cleavages (e.g. Ser or Thr) results in the normal alpha and beta backbone cleavages being reduced in comparison to those cleavages which originate from side chains.
含有天冬氨酸（Asp）和/或谷氨酸（Glu）的多种天然和合成两栖类肽的M - H离子的碰撞诱导光谱显示出特征性的γ主链裂解离子，这些离子可确定这些残基在肽中的位置。一项理论研究表明，谷氨酸的裂解涉及来自谷氨酸α侧链的羧酸根阴离子的亲核取代内环化反应（S(N)i反应），以形成去质子化的环状内酯。天冬氨酸或谷氨酸或其他导致明显侧链裂解的残基（如丝氨酸或苏氨酸）的存在，与源自侧链的裂解相比，会使正常的α和β主链裂解减少。
