Further studies of in-source fragmentation of peptides in matrix-assisted laser desorption-ionization
Further studies of in-source fragmentation of peptides in matrix-assisted laser desorption-ionization
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DOI：
10.1016/s0168-1176(97)00217-6
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发表时间：
1997-12-01
影响因子：
1.8
通讯作者：
Reiber, DC
中科院分区：
文献类型：
--
作者：
Brown, RS;Feng, JH;Reiber, DC
已经研究了影响 MALDI 离子化肽的源内裂解的多种其他因素。为了进一步了解这种源内碎裂过程，我们检查了解吸激光脉冲宽度和波长以及离子提取延迟时间等仪器参数对肽碎裂的影响。使用较短的解吸波长 (266 nm) 会增加源内碎片离子的强度（相对于完整的质子化分子离子种类），但不会改变观察到的碎片离子系列的类型。本质上，当激光脉冲宽度变化（700 ps 与 5 ns）并且采用恒定（337 nm）解吸波长时，没有观察到碎片光谱的差异。此外，还检查了几种基质的正离子和负离子源内碎片光谱。先前报道的 c(n) 和 y(n) 源内碎片离子系列在正离子和负离子模式 MALDI 光谱中的出现和强度非常相似。正离子和负离子质谱的这种相似性表明，源内碎裂很可能独立于电离途径（质子化或去质子化）而发生，因此与先前建议的质子转移反应的“放热性”无关。讨论了可能的替代离子活化过程。还鉴定出一种新的“a(n) 型”离子碎片系列，并且在某些类别的 MALDI 基质中更为普遍。最后，某些 MALDI 矩阵可以抑制源内碎片。相对于 DHB，Super-DHB 几乎完全抑制 y(n) 系列碎片离子。 c(n) 系列碎片离子的相对强度也有所降低，但仍然可以观察到。 α-氰基-3,4,5-三甲氧基肉桂酸几乎完全抑制 c(n) 和 y(n) 碎裂离子系列。 (C) 1997 Elsevier Science B.V.
A variety of additional factors that influence the in-source fragmentation of MALDI ionized peptides have been studied. In an attempt to further understand this in-source fragmentation process, instrumental parameters such as the desorption laser pulse width and wavelength, and ion-extraction delay period have been examined as to their effect on peptide fragmentation. Use of a shorter desorption wavelength (266 nm) increases the intensity of in-source fragment ions (relative to the intact protonated molecular ion species), but does not change the types of fragment ion series that are observed. Essentially, no differences in the fragmentation spectra were observed when the laser pulse width was varied (700 ps versus 5 ns) and a constant (337 nm) desorption wavelength was employed. In addition, both positive-and negative-ion in-source fragmentation spectra for several matrices were examined. The previously reported c(n) and y(n) in-source fragment ion series are very similar as to occurrence and intensity in both positive-and negative-ion mode MALDI spectra. This similarity in positive-and negative-ion mass spectra suggests that in-source fragmentation most probably occurs independent of the ionization pathway (protonation or deprotonation) and is therefore not linked to the "exothermicity" of the proton transfer reaction as previously suggested. Possible alternative ion activation processes are discussed. A new "a(n)-type" ion fragment series has also been identified and is more prevalent with certain classes of MALDI matrices. Finally, in-source fragmentation can be suppressed by certain MALDI matrices. Super-DHB almost completely suppresses y(n)-series fragment ions relative to DHB. The c(n)-series fragment ions are also reduced in relative intensity but are still observed. Alpha-cyano-3,4,5-trimethoxy cinnamic acid is shown to almost completely suppress both of the c(n) and y(n) fragmentation ion series. (C) 1997 Elsevier Science B.V.