Side Chain Driven Mass Spectral Fragmentation of Lys Containing Peptides: Cα-CO Bond Cleavage in Xxx-Lys-Xxx Sequences

IF 2.7 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS
Sanjeev Kumar, , , Marimuthu Vijayasarathy, , , Venkatesha M. Achanna, , and , Padmanabhan Balaram*, 
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Abstract

Mass spectral fragmentation of the tripeptide amide Ala-Lys-Ala-amide (AKA*) yields a product ion at m/z 228.1, which corresponds to a neutral loss of 43 Da from the b3 ion (m/z 271.1). Similar losses of 43 Da are observed from bn ions in the hexapeptide AKAAKA* and tetrapeptide AKAA*. The role of the Lys2 residue, in mediating the neutral loss, is supported by the absence of the corresponding product ion in the MS2 spectrum of AVA* and attenuation of the intensity in analogs containing ornithine/diaminobutyric acid residues at position 2. The role of the N-terminus amino group is suggested by the absence of this neutral loss when the residue Ala1 amino group is acetylated or dimethylated. In XKA* sequences, where X = Gly, Ala, Leu, Aib and Pro, the observed neutral losses from b3 are 29, 43, 85, 57, and 69 Da, respectively, indicative of Cα-CO bond cleavage releasing the R-CH = NH fragment. Isotope labeling and comparison with mass spectral fragments generated from synthetic Nα-formyl Lys-Ala-amide (fKA*) establish the identity of the ion at m/z 228 in the MS2 spectrum of AKA* as the b ion [fKA]. A charge remote fragmentation pathway, involving proton abstraction from the terminal amino group, by the Lys2 ε amino group, followed by Cα-CO bond cleavage, is proposed as a plausible mechanism for the observed noncanonical cleavage process.

Abstract Image

含赖氨酸肽的侧链驱动质谱碎片化:xxx -赖氨酸- xxx序列中的Cα-CO键断裂。
三肽酰胺Ala-Lys-Ala-amide (AKA*)的质谱破碎产生一个m/z 228.1的产物离子,对应于b3离子(m/z 271.1)的43 Da的中性损失。在六肽AKAAKA*和四肽AKAA*中的十亿离子中观察到类似的43 Da损失。在AVA*的MS2光谱中缺少相应的产物离子,并且在2位含有鸟氨酸/二氨基丁酸残基的类似物中强度衰减,支持了Lys2残基介导中性损失的作用。当残基Ala1氨基被乙酰化或二甲基化时,没有这种中性损失,表明n端氨基的作用。在X = Gly, Ala, Leu, Aib和Pro的XKA*序列中,b3的中性损失分别为29,43,85,57和69 Da,表明c - α- co键断裂释放R-CH = NH片段。同位素标记并与合成的n α-甲酰基Lys-Ala-amide (fKA*)产生的质谱片段比较,确定了AKA* MS2谱中m/z 228处的离子为b离子[fKA]。研究人员提出了一种电荷远程断裂途径,即质子被Lys2 ε基团从末端氨基抽离,然后被Cα-CO键切割,这可能是观察到的非典型裂解过程的一种可行机制。
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来源期刊
CiteScore
5.50
自引率
9.40%
发文量
257
审稿时长
1 months
期刊介绍: The Journal of the American Society for Mass Spectrometry presents research papers covering all aspects of mass spectrometry, incorporating coverage of fields of scientific inquiry in which mass spectrometry can play a role. Comprehensive in scope, the journal publishes papers on both fundamentals and applications of mass spectrometry. Fundamental subjects include instrumentation principles, design, and demonstration, structures and chemical properties of gas-phase ions, studies of thermodynamic properties, ion spectroscopy, chemical kinetics, mechanisms of ionization, theories of ion fragmentation, cluster ions, and potential energy surfaces. In addition to full papers, the journal offers Communications, Application Notes, and Accounts and Perspectives
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