Medzihradszky K F, Guan S, Maltby D A, Burlingame A L
Mass Spectrometry Facility, Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143-0446, USA.
J Am Soc Mass Spectrom. 2007 Sep;18(9):1617-24. doi: 10.1016/j.jasms.2007.06.002. Epub 2007 Jun 19.
Sulfopeptides can be misassigned as phosphopeptides because of the isobaric nature of the sulfo- and the phosphomoieties. Instruments having the ability to measure mass with high accuracy may be employed to distinguish these moieties based on their mass defect (the sulfo-group is 9 mmu lighter than the phosphomoiety). However, the assignment of the exact site(s) of post-translational modification is required to probe biological function. We have reported earlier that peptides with identical sequences containing either O-sulfo- or O-phospho-modifications display different fragmentation behavior (K. F. Medzihradszky et al., Mol. Cell. Proteom.2004, 3, 429-440). We have also established that O-sulfo moieties are susceptible to side-chain fragmentation during collision-induced dissociation. Our present study provides evidence that neutral SO(3) losses can also occur in electron capture dissociation and electron-transfer dissociation experiments. We also report that such neutral losses may be reduced by fragmenting peptide-alkali metal adducts, such as sodiated or potassiated peptides.
由于磺酸基和磷酸基团的等压性质，硫肽可能会被误鉴定为磷酸肽。可以使用具有高精度质量测量能力的仪器，根据它们的质量缺陷来区分这些基团（磺酸基比磷酸基团轻9毫微米）。然而，需要确定翻译后修饰的确切位点，以探究其生物学功能。我们之前曾报道，具有相同序列的含有O-磺酸基或O-磷酸基修饰的肽，表现出不同的碎片化行为（K. F. 梅齐赫拉德斯基等人，《分子与细胞蛋白质组学》，2004年，第3卷，第429 - 440页）。我们还证实，O-磺酸基团在碰撞诱导解离过程中容易发生侧链碎片化。我们目前的研究表明，在电子捕获解离和电子转移解离实验中也会发生中性SO(3)损失。我们还报告说，通过使肽 - 碱金属加合物（如钠化或钾化肽）碎片化，可以减少这种中性损失。
