Kovalyov Sergey V, Zhokhov Sergey S, Onoprienko Ludmila V, Vaskovsky Boris V, Lebedev Albert T
1 Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow, Russia.
2 Shemyakin-Ovchinnikov Insitiute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Eur J Mass Spectrom (Chichester). 2017 Dec;23(6):376-384. doi: 10.1177/1469066717730705. Epub 2017 Sep 7.
Electron-transfer dissociation (ETD) and electron-transfer and higher-energy collision dissociation (EThcD) spectra of short tryptic peptides with leucine/isoleucine residues in neighboring positions demonstrate intensive w-ions. On the contrary, u-ions possess very low intensities (if present at all). Therefore radical site migration is negligible in the applied conditions while ETD (EThcD) spectra allow for the reliable discrimination of the isomeric residues in the sequencing process. The presence of a fragment ion 43.055 mass units lower than z-ion of peptides with IK sequence at their C-termini was shown to be a result of alternative fragmentation starting from the loss of propylammonium ion from the doubly protonated peptide molecule and formation of an oxazole fragment ion.
在相邻位置含有亮氨酸/异亮氨酸残基的短胰蛋白酶肽的电子转移解离（ETD）以及电子转移和高能碰撞解离（EThcD）光谱显示出强烈的w离子。相反，u离子的强度非常低（如果存在的话）。因此，在所应用的条件下，自由基位点迁移可忽略不计，而ETD（EThcD）光谱在测序过程中能够可靠地区分异构残基。结果表明，在其C末端，肽的z离子质量单位低43.055的碎片离子的存在是由于双质子化肽分子中丙基铵离子的丢失以及恶唑碎片离子的形成导致的替代碎片化的结果。
