作者:Yun Zhang、Hao Zhang、Weidong Cui、Hao Chen
DOI:10.1007/s13361-011-0170-4
日期:2011.9.1
Our previous study showed that selenamide reagents such as ebselen and N-(phenylseleno)phthalimide (NPSP) can be used for selective and rapid derivatization of protein/peptide thiols in high conversion yield. This paper reports the systematic investigation of MS/MS dissociation behaviors of selenamide-derivatized peptide ions upon collision induced dissociation (CID) and electron transfer dissociation (ETD). In the positive ion mode, derivatized peptide ions exhibit tag-dependent CID dissociation pathways. For instance, ebselen-derivatized peptide ions preferentially undergo Se–S bond cleavage upon CID to produce a characteristic fragment ion, the protonated ebselen (m/z 276), which allows selective identification of thiol peptides from protein digest as well as selective detection of thiol proteins from protein mixture using precursor ion scan (PIS). In contrast, NPSP-derivatized peptide ions retain their phenylselenenyl tags during CID, which is useful in sequencing peptides and locating cysteine residues. In the negative ion CID mode, both types of tags are preferentially lost via the Se–S cleavage, analogous to the S–S bond cleavage during CID of disulfide-containing peptide anions. In consideration of the convenience in preparing selenamide-derivatized peptides and the similarity of Se–S of the tag to the S–S bond, we also examined ETD of the derivatized peptide ions to probe the mechanism for electron-based ion dissociation. Interestingly, facile cleavage of Se–S bond occurs to the peptide ions carrying either protons or alkali metal ions, while backbone cleavage to form c/z ions is severely inhibited. These results are in agreement with the Utah-Washington mechanism proposed for depicting electron-based ion dissociation processes.
我们之前的研究表明,硒酰胺试剂如依布硒啉和N-(苯基硒基)邻苯二甲酰亚胺(NPSP)可用于蛋白质/肽硫醇的选择性、快速衍生化,且转化率高。本文报道了硒酰胺衍生肽离子在碰撞诱导解离 (CID) 和电子转移解离 (ETD) 下的 MS/MS 解离行为的系统研究。在正离子模式下,衍生肽离子表现出标签依赖性 CID 解离途径。例如,依布硒啉衍生的肽离子在 CID 上优先经历 Se-S 键裂解,产生特征片段离子,即质子化的依布硒啉 (m/z 276),它可以选择性识别蛋白质消化物中的硫醇肽,并选择性检测使用前体离子扫描 (PIS) 从蛋白质混合物中提取硫醇蛋白。相比之下,NPSP 衍生的肽离子在 CID 过程中保留其苯基硒基标签,这对于肽测序和定位半胱氨酸残基非常有用。在负离子 CID 模式下,两种类型的标签都会优先通过 Se-S 裂解而丢失,类似于含二硫键的肽阴离子 CID 期间的 S-S 键裂解。考虑到制备硒酰胺衍生肽的便利性以及标签中Se-S与S-S键的相似性,我们还检查了衍生肽离子的ETD,以探讨基于电子的离子解离机制。有趣的是,携带质子或碱金属离子的肽离子容易发生 Se-S 键的断裂,而形成 c/z 离子的主链断裂则受到严重抑制。这些结果与为描述基于电子的离子解离过程而提出的犹他-华盛顿机制一致。