Cα-C backbone fragmentation dominates in electron detachment dissociation of gas-phase polypeptide polyanions
Cα-C backbone fragmentation dominates in electron detachment dissociation of gas-phase polypeptide polyanions
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DOI：
10.1002/chem.200400806
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发表时间：
2005-03-04
影响因子：
4.3
通讯作者：
Zubarev, RA
中科院分区：
文献类型：
--
作者：
Kjeldsen, F;Silivra, OA;Zubarev, RA
用大于10eV的电子辐照去质子化的多肽[M-nH]（n-），可诱导多肽聚阴离子的电子解离（EDD）断裂。已发现EDD优先导致a（.）和x个碎片离子（C. - C骨架裂解）所产生的解离的氧化自由基阴离子[M-nH]（n-1）-.）。我们证明了C. -在串联质谱中很少观察到的C裂解可以解释大部分骨架断裂，其中偶数电子X片段在自由基a（.）离子。在B3LYP理论水平上用6 - 311 + G（2p，2d）//6 - 31 + G（d，p）基组进行的从头计算表明EDD的单向机制（切割总是在自由基位点的N端），其中a（.），x形成优于a，x（.）裂解率为74.2 kJ mol（-1）。因此，骨架C-a-C键N-末端的脯氨酸残基应免疫EDD，与观察结果一致。EDD可以在质谱中应用于诸如肽测序和不稳定的翻译后修饰的定位等任务，例如，通过硫酸化和磷酸化引入的那些。EDD现在不仅可以在傅立叶变换质谱中进行，而且可以在更广泛使用的四极（Paul）离子阱中进行。
Fragmentation of peptide polyanions by electron detachment dissociation (EDD) has been induced by electron irradiation of deprotonated polypeptides [M-nH](n-) with > 10eV electrons. EDD has been found to lead preferentially to a(.) and x fragment ions (C.-C backbone cleavage) arising from the dissociation of oxidized radical anions [M-nH]((n-1)-.). We demonstrate that C.-C cleavages, which are otherwise rarely observed in tandem mass spectrometry, can account for most of the backbone fragmentation, with even-electron x fragments dominating over radical a(.) ions. Ab initio calculations at the B3LYP level of theory with the 6-311 + G (2p,2d)//6-31 + G(d,p) basis set suggested a unidirectional mechanism for EDD (cleavage always N-terminal to the radical site), with a(.),x formation being favored over a,x(.) fragmentation by 74.2 kJ mol(-1). Thus, backbone C-a-C bonds N-terminal to proline residues should be immune to EDD, in agreement with the observations. EDD may find application in mass spectrometry for such tasks as peptide sequencing and localization of labile post-translational modifications, for example, those introduced by sulfation and phosphorylation. EDD can now be performed not only in Fourier transform mass spectrometry, but also in far more widely used quadrupole (Paul) ion traps.