Department of Chemistry, Purdue University, West Lafayette, Indiana 47907-1393, USA.
Anal Chem. 2010 Apr 1;82(7):2856-64. doi: 10.1021/ac9028328.
Cleavage of the disulfide bond within a polypeptide was observed when the nanoelectrospray (nanoESI) plume of a peptide solution interacted with a low-temperature helium plasma in air. Online mass spectrometric analysis revealed that chain separation accompanied by a mass increase of 1 or 16 Da for each chain was common to peptides having an interchain disulfide bond, while for peptides having intrachain disulfide bonds, the reaction products typically showed mass increases of 17 Da. Experimental results suggested that hydroxyl radicals initiated from the plasma were likely to be responsible via dissociative addition to the disulfide bond (RSSR'), giving rise to RSH and R'SO*. When the hydroxyl radical addition product ions (M + nH + OH, n is the charge state) generated from peptides having intrachain peptides were subjected to collision-induced dissociation (CID) in an ion trap, a-, b-, and y-type sequence ions within the cyclic structure defined by the disulfide bond were observed in addition to the exocyclic cleavages typically seen from CID of M + nH peptide ions. Rich structural information could thus be obtained. These findings were demonstrated in 14 peptides containing disulfide bonds and further by bovine insulin, which has three disulfide bonds. Collisional activation of the M + 5H + OH insulin ions provided 76% of the possible backbone cleavages as compared to 26% acquired from CID of the M + 5H ions.
当多肽溶液的纳喷雾（nanoESI）羽流与空气中的低温氦等离子体相互作用时，观察到二硫键在多肽内的断裂。在线质谱分析表明，对于具有链间二硫键的肽，常见的是伴随着每个链的质量增加 1 或 16 Da 的链分离，而对于具有链内二硫键的肽，反应产物通常显示质量增加 17 Da。实验结果表明，等离子体中引发的羟基自由基可能通过对二硫键（RSSR'）的解离加成来负责，生成 RSH 和 R'SO*。当来自具有链内肽的肽的羟基自由基加成产物离子 (M + nH + OH, n 是电荷态) 在离子阱中进行碰撞诱导解离 (CID) 时，除了通常从 M + nH 肽离子的 CID 中看到的外环裂解外，还观察到由二硫键定义的环状结构内的 a-、b- 和 y-型序列离子。因此，可以获得丰富的结构信息。这些发现通过含有二硫键的 14 种肽进一步证明，并且通过具有三个二硫键的牛胰岛素进一步证明。与从 M + 5H 离子的 CID 获得的 26%相比，M + 5H + OH 胰岛素离子的碰撞激活提供了 76%的可能的骨架裂解。
