Investigation of several unique tandem mass spectrometric fragmentation patterns of NFDEIDR, an orcokinin analog, and its N-terminal dimethylated form
Investigation of several unique tandem mass spectrometric fragmentation patterns of NFDEIDR, an orcokinin analog, and its N-terminal dimethylated form
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DOI：
10.1002/rcm.2337
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发表时间：
2006-01-01
影响因子：
2
通讯作者：
Li, LJ
中科院分区：
文献类型：
--
作者：
Fu, Q;Li, LJ
奥可激肽是一个亲肌性神经肽家族，广泛存在于各种十足类甲壳类动物和昆虫中。到目前为止，大多数已鉴定的orcokinins在它们的N端都有一个保守的NFDEIDR序列。电喷雾电离四极杆飞行时间串联质谱仪(ESI-QTOF-MS/MS)对双电荷态奥可可碱前体离子的分析表明，存在一个比y((n-1))离子更强的y((n-1))+10峰。为了阐明这种新的碎片离子的特性和理解这种碎片的机制，我们使用了一种结合的方法，包括同位素N-端二甲基化、甲酯化和同位素编码的NFDEIDR。通过比较这些化学修饰的鸟苷类似物的碎裂模式，可以确定y((n-1))+10离子的结构为y((n-1))+CO-H2O。在NFDEIDR和其他几个多肽的MS/MS谱中，也存在y(X)+CO-H2O离子，以及y(X)+CO和y(X)+CONH3离子。此外，我们还报道了N-端二甲基NFDEIDR(2+)的MS/MS谱中另外两个不寻常的碎裂离子，它们产生了新的碎片离子y((n-1))+38离子和[M+2H-59](2+)离子。这两个离子系列涉及天冬酰胺侧链的中性损失。同样的离子也存在于N端带有二甲基天冬酰胺的其他多肽中。介绍了二甲胺侧链损失与二甲胺损失之间的竞争关系。还报道了N-端二甲基天冬氨酸(1)侧链的丢失。我们还首次报道了天冬氨酸(1)N-末端氨基的中性损失和天冬氨酸侧链的二氧化碳损失。版权所有(C)2006 John Wiley&Sons，Ltd.
Orcokinins are a family of myotropic neuropeptides widely present in various decapod crustaceans and insect species. The majority of the orcokinins identified to date share a conserved sequence of NFDEIDR at their N-termini. Electrospray ionization quadrupole time-of-flight tandem mass spectrometric (ESI-QTOF-MS/MS) analysis of doubly charged orcokinin precursor ions reveals the presence of a y((n-1)) + 10 peak, which is more intense than that for the y((n-1)) ion. To elucidate the identity of this novel fragment ion and understand the mechanism underlying this fragmentation, we employed a combined approach involving the use of isotopic N-terminal dimethylation, methyl esterification, and isotope-encoded NFDEIDR. Comparison of the fragmentation patterns of these chemically modified orcokinin analogs allowed the determination of the structure of the y((n-1)) + 10 ion as y((n-1)) + CO-H2O. The y(x) + CO-H2O ions, along with the y(x) + CO and y(x) + CONH3 ions, are also present in the MS/MS spectra of NFDEIDR and several other peptides. Additionally, we report two other unusual fragmentation ions in the MS/MS spectra of N-terminal dimethyl NFDEIDR (2+), which yields the novel fragment ions of the y((n-1)) + 38 ion and the [M+2H-59](2+) ion. These two ion series involve the neutral loss of the asparagine side chain. The same sets of ions are also present in other peptides with dimethyl-modified asparagines at the N-terminus. The competition between the side-chain loss and loss of dimethylamine is described. The loss of the side chain of N-terminal dimethyl Asp(1) is reported as well. We also report for the first time the neutral loss of ammonia from the N-terminal amino group of Asn(1) and the loss Of CO2 from the side chain of aspartic acid. Copyright (c) 2006 John Wiley & Sons, Ltd.