Near-UV Photodissociation of Tryptic Peptide Cation Radicals. Scope and Effects of Amino Acid Residues and Radical Sites
Near-UV Photodissociation of Tryptic Peptide Cation Radicals. Scope and Effects of Amino Acid Residues and Radical Sites
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DOI：
10.1007/s13361-016-1586-7
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发表时间：
2017-02
影响因子：
3.2
通讯作者：
H. T. Nguyen;F. Tureček
中科院分区：
文献类型：
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作者：
H. T. Nguyen;F. Tureček
用电子转移解离法制备了Z型[Axar+]、[AXAK+]和[XAR+]的多肽阳离子碎片离子，其中X=A、C、D、E、F、G、H、K、L、M、N、P、Y和W，并用355 nm波长处的近紫外光解离对其进行了研究。激光脉冲依赖性测量表明，除苯丙氨酸外，大多数X残基的离子布居都是均匀的。UVPD导致主链CO─NH键解离，伴随着氢原子转移，产生[YN]+类型的碎片离子。与碰撞诱导解离相比，UVPD产生的侧链解离较少，即使是对自由基诱导的侧链断裂敏感的残基也是如此。主链解离是由与355 nm光子能量共振的多肽离子R-CH-ConH-发色团中第二(B)激发电子态的跃迁引发的。电子促进增加了B激发态的极性，R-CH+-C(O-)NH-，并通过从接近酸性的Cα和酰胺氮位置转移质子来引导反应进行。
Peptide cation-radical fragment ions of the z-type, [●AXAR+], [●AXAK+], and [●XAR+], where X = A, C, D, E, F, G, H, K, L, M, N, P, Y, and W, were generated by electron transfer dissociation of peptide dications and investigated by MS3-near-ultraviolet photodissociation (UVPD) at 355 nm. Laser-pulse dependence measurements indicated that the ion populations were homogeneous for most X residues except phenylalanine. UVPD resulted in dissociations of backbone CO─NH bonds that were accompanied by hydrogen atom transfer, producing fragment ions of the [yn]+type. Compared with collision-induced dissociation, UVPD yielded less side-chain dissociations even for residues that are sensitive to radical-induced side-chain bond cleavages. The backbone dissociations are triggered by transitions to second (B) excited electronic states in the peptide ion R-CH●-CONH- chromophores that are resonant with the 355-nm photon energy. Electron promotion increases the polarity of theBexcited states, R-CH+-C●(O–)NH-, and steers the reaction to proceed by transfer of protons from proximate acidic Cαand amide nitrogen positions.