Chemistry Department and GIGA-R, Mass Spectrometry Laboratory, University of Liege, Belgium.
J Phys Chem B. 2013 Feb 28;117(8):2321-7. doi: 10.1021/jp311464k. Epub 2013 Feb 13.
The early mechanisms of matrix-assisted laser desorption/ionization in-source decay (MALDI-ISD) are described herein. MALDI-ISD is initiated by the hydrogen transfer from excited matrix molecules to the carbonyl oxygen of the peptide backbone, which is followed by a radical-induced cleavage, producing the c'/z• fragment pair. As expected, the use of 2,5-DHB or 1,5-DAN was efficient to induce MALDI-ISD, and the strongest intensity of MALDI-ISD fragments was observed when laser shots were performed on matrix crystals. In contrast, the hydrogen radical transfer reaction was suppressed by using ionic liquid and amorphous structure of 2,5-DHB and 1,5-DAN mixture as a matrix. Our results suggest that the hydrogen transfer occurs on the matrix crystal during the dissipation of the laser energy and before desorption, following ISD fragments formed in the MALDI plume.
本文描述了基质辅助激光解吸/电离源内降解（MALDI-ISD）的早期机制。MALDI-ISD 是由激发态基质分子向肽骨架羰基氧的氢转移引发的，随后是自由基诱导的裂解，产生 c'/z• 片段对。正如预期的那样，使用 2,5-DHB 或 1,5-DAN 有效地诱导了 MALDI-ISD，并且当在基质晶体上进行激光射击时观察到 MALDI-ISD 片段的最强强度。相比之下，通过使用离子液体和 2,5-DHB 和 1,5-DAN 混合物的无定形结构作为基质，抑制了氢自由基转移反应。我们的结果表明，氢转移发生在激光能量耗散期间和解吸之前的基质晶体上，随后在 MALDI 羽流中形成 ISD 片段。
