Tandem electrospray mass spectrometric studies of proton and sodium ion adducts of neutral peptides with modified N- and C-termini: synthetic model peptides and microheterogeneous peptaibol antibiotics
Tandem electrospray mass spectrometric studies of proton and sodium ion adducts of neutral peptides with modified N- and C-termini: synthetic model peptides and microheterogeneous peptaibol antibiotics
复制标题
DOI：
10.1002/rcm.2349
复制
发表时间：
2006-01-01
影响因子：
2
通讯作者：
Balaram, P
中科院分区：
文献类型：
--
作者：
Sabareesh, V;Balaram, P
用电喷雾离子阱质谱研究了N-和C-末端封闭的中性肽的[M+H]（+）和[M+Na]（+）加合物的裂解。这些合成设计的肽的N-末端用叔丁氧基羰基（Boc）封闭，并且C-末端被酯化。这些肽不具有能够络合的侧链，因此骨架酰胺单元是质子化和金属化的唯一位点。质子化肽的裂解模式与钠离子加合物的裂解模式显著不同。虽然在[M+Na]+的MS/MS的情况下很容易发生N-末端封闭基团的损失，但在[M+H]+的MS/MS的情况下，C-末端甲氧基的裂解似乎是一个容易的过程。质子化加合物的碎裂仅产生B（n）离子，而y（n）和a.离子主要由钠离子加合物的碎裂形成。由[M+Na]+的断裂产生的α离子缺乏N-末端Boc基团（并且在此称为α（n）* 离子）。[M+Na]+物质的MS/MS也产生了强度显著较低的bn离子，其缺乏N-末端Boc基团（B（n）*）。在具有N-末端乙酰基的肽的情况下，观察到质子和钠离子加合物的断裂模式之间的类似区别。来自木霉属物种的天然存在的peptaibol的H+和Na+加合物的片段化的实例证实，这两种离子化物质的片段化产生互补信息，可用于对天然肽进行测序。对来自肽的[M+H]（+）加合物的B（n）离子的同位素模式的检查提供了对微不均匀样品序列的了解。该研究表明，质子化和钠离子加合物的组合使用应证明在肽的从头测序中是有用的，特别是具有修饰的N-和C-末端的天然存在的中性肽，例如，肽。版权所有（c）2006约翰威利父子有限公司。
The fragmentations of [M+H](+) and [M+Na](+) adducts of neutral peptides with blocked N- and C-termini have been investigated using electrospray ion trap mass spectrometry. The N-termini of these synthetically designed peptides are blocked with a tertiarybutyloxycarbonyl (Boc) group, and the C-termini are esterified. These peptides do not possess side chains that are capable of complexation and hence the backbone amide units are the sole sites of protonation and metallation. The cleavage patterns of the protonated peptides are strikingly different from those of sodium ion adducts. While the loss of the N-terminal blocking group occurs quite readily in the case of MS/MS of [M+Na]+, the cleavage of the C-terminal methoxy group seems to be a facile process in the case of MS/MS of [M+H]+. Fragmentation of the protonated adducts yields only b(n) ions, while y(n) and a. ions are predominantly formed from the fragmentation of sodium ion adducts. The an ions arising from the fragmentation of [M+Na]+ lack the N-terminal Boc group (and are here termed a(n)* ions). MS/MS of [M+Na]+ species also yields bn ions of substantially lower intensities that lack the N-terminal Boc group (b(n)*). A similar distinction between the fragmentation patterns of proton and sodium ion adducts is observed in the case of peptides possessing an N-terminal acetyl group. An example of the fragmentation of the H+ and Na+ adducts of a naturally occurring peptaibol from a Trichoderma species confirms that fragmentation of these two ionized species yields complementary information, useful in sequencing natural peptides. Inspection of the isotopic pattern of b(n) ions derived from [M+H](+) adducts of peptaibols provided insights into the sequences of microheterogeneous samples. This study reveals that the combined use of protonated and sodium ion adducts should prove useful in de novo sequencing of peptides, particularly of naturally occurring neutral peptides with modified N- and C-termini, for example, peptaibols. Copyright (c) 2006 John Wiley & Sons, Ltd.