Structure of [M + H - H2O]+ from Protonated Tetraglycine Revealed by Tandem Mass Spectrometry and IRMPD Spectroscopy
Structure of [M + H - H2O]+ from Protonated Tetraglycine Revealed by Tandem Mass Spectrometry and IRMPD Spectroscopy
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DOI：
10.1021/jp9113046
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发表时间：
2010-04-22
影响因子：
2.9
通讯作者：
Van Stipdonk, Michael J.
中科院分区：
文献类型：
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作者：
Bythell, Benjamin J.;Dain, Ryan P.;Van Stipdonk, Michael J.
使用多级串联质谱和碰撞诱导解离来研究 GGGX（其中 X = G、A 和 V）、GGGGG 和这些肽的甲酯的质子化版本中 H2O 或 CH3OH 的损失。此外，使用波长选择性红外多光子解离来表征源自质子化 GGGG 的 [M + H - H2O](+) 产物以及该峰的主要 MS3 片段 [M + H - H2O - 29](+)。与早期的工作一致 [Ballard, K. D.；加斯克尔，S.J.J.Am。苏克。质谱。 1993, 4, 477-481;里德，G.E.；辛普森，R.J.；奥海尔，R.A.J.国际..J.质谱。 1999, 190/191, 209-230000]，CID 实验表明 [M + H - H2O](+) 是质子化 GGGG 和质子化 GGGG-OMe 产生的主峰。这强烈表明 H2O 分子的损失发生在 C 末端游离酸以外的位置，并且产物不对应于 b(4) 离子的形成。随后的 [M + H - H2O](+) CID 通过产生比母离子少 29 个质量单位的主要产物来支持这一提议。这与 HN=CH2 的损失而不是一氧化碳（28 质量单位）的损失一致，这是恶唑酮型 b(n) 离子的特征。实验和理论红外光谱或一组可能的结构之间的比较证实，[M + H - H2O](+) 峰不是取代的恶唑酮，而是表明形成了一种离子，该离子沿着肽主链、靠近弹药末端形成了一个五元环。此外。 [M + H - H2O - 29](+) 峰的过渡结构计算以及理论和实验光谱的比较也支持了这一建议。
Multiple-stage tandem mass spectrometry and collision-induced dissociation were used to investigate loss of H2O or CH3OH from protonated versions of GGGX (where X = G, A, and V), GGGGG, and the methyl esters of these peptides. In addition, wavelength-selective infrared multiple photon dissociation was used to characterize the [M + H - H2O](+) product derived from protonated GGGG and the major MS3 fragment, [M + H - H2O - 29](+) of this peak. Consistent with the earlier work [Ballard, K. D.; Gaskell, S. J. J. Am. Soc. Mass Spectrom. 1993, 4, 477-481; Reid, G. E.; Simpson, R. J.; O'Hair, R. A. J. Int..J. Mass Spectrom. 1999, 190/191, 209-230000], CID experiments show that [M + H - H2O](+) is the dominant peak generated from both protonated GGGG and protonated GGGG-OMe. This strongly suggests that the loss of the H2O molecule occurs from a position other than the C-terminal free acid and that the product does not correspond to formation of the b(4) ion. Subsequent CID of [M + H - H2O](+) supports this proposal by resulting in a major product that is 29 mass units less than the precursor ion. This is consistent with loss of HN=CH2 rather than loss of carbon monoxide (28 mass units), which is characteristic of oxazolone-type b(n) ions. Comparison between experimental and theoretical infrared spectra ''or a group of possible structures confirms that the [M + H - H2O](+) peak is not a substituted oxazolone but instead suggests formation of an ion that features a five-membered ring along the peptide backbone, close to the ammo terminus. Additionally. transition structure calculations and comparison of theoretical and experimental spectra of the [M + H - H2O - 29](+) peak also support this proposal.