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首页> 外文期刊>Journal of mass spectrometry: JMS >Characterization of N-methylated amino acids by GC-MS after ethyl chloroformate derivatization
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Characterization of N-methylated amino acids by GC-MS after ethyl chloroformate derivatization

机译：氯甲酸乙酯衍生化后的GC-MS表征N-甲基化氨基酸

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Methylation is an essential metabolic process in the biological systems, and it is significant for several biological reactions in living organisms. Methylated compounds are known to be involved in most of the bodily functions, and some of them serve as biomarkers. Theoretically, all a-amino acids can be methylated, and it is possible to encounter them in most animal/plant samples. But the analytical data, especially the mass spectral data, are available only for a few of the methylated amino acids. Thus, it is essential to generate mass spectral data and to develop mass spectrometry methods for the identification of all possible methylated amino acids for future metabolomic studies. In this study, all N-methyl and N,N-dimethyl amino acids were synthesized by the methylation of a-amino acids and characterized by a GC-MS method. The methylated amino acids were derivatized with ethyl chloroformate and analyzed by GC-MS under EI and methane/CI conditions. The EI mass spectra of ethyl chloroformate derivatives of N-methyl (1-18) and N, N-dimethyl amino acids (19-35) showed abundant [M-COOC2H5](+) ions. The fragment ions due to loss of C2H4, CO2, (CO2 + C2H4) from[M-COOC2H5](+) were of structure indicative for 1-18. The EI spectra of 19-35 showed less number of fragment ions when compared with those of 1-18. The side chain group (R) caused specific fragment ions characteristic to its structure. The methane/CI spectra of the studied compounds showed [M + H](+) ions to substantiate their molecular weights. The detected EI fragment ions were characteristic of the structure that made easy identification of the studied compounds, including isomeric/isobaric compounds. Fragmentation patterns of the studied compounds (1-35) were confirmed by high-resolution mass spectra data and further substantiated by the data obtained from C-13(2)-labeled glycines and N-ethoxycarbonyl methoxy esters. The method was applied to human plasma samples for the identification of amino acids and methylated amino acids. Copyright (C) 2016 John Wiley & Sons, Ltd.
机译：甲基化是生物系统中必不可少的代谢过程，对于活生物体中的几种生物反应而言都非常重要。已知甲基化的化合物与大多数身体功能有关，其中一些充当生物标记。从理论上讲，所有α-氨基酸都可以被甲基化，并且在大多数动植物样品中都可能遇到它们。但是分析数据，尤其是质谱数据，仅可用于少数甲基化氨基酸。因此，至关重要的是产生质谱数据并开发质谱方法以鉴定所有可能的甲基化氨基酸，以用于未来的代谢组学研究。在这项研究中，所有的N-甲基和N，N-二甲基氨基酸都是通过α-氨基酸的甲基化合成的，并通过GC-MS方法进行了表征。用氯甲酸乙酯将甲基化的氨基酸衍生化，并在EI和甲烷/ CI条件下通过GC-MS分析。 N-甲基（1-18）和N，N-二甲基氨基酸（19-35）的氯甲酸乙酯衍生物的EI质谱显示出丰富的[M-COOC2H5]（+）离子。由[M-COOC2H5]（+）中的C2H4，CO2，（CO2 + C2H4）损失引起的碎片离子具有指示1-18的结构。与1-18相比，19-35的EI光谱显示碎片离子数量少。侧链基团（R）引起其结构特征性的特定碎片离子。所研究化合物的甲烷/ CI光谱显示[M + H]（+）离子可证实其分子量。检测到的EI碎片离子具有易于鉴定所研究化合物（包括同分异构/等压化合物）的结构特征。通过高分辨率质谱数据确认了所研究化合物（1-35）的碎片模式，并进一步从C-13（2）标记的甘氨酸和N-乙氧基羰基甲氧基酯获得的数据进一步证实了该化合物的碎片模式。该方法适用于人体血浆样品中氨基酸和甲基化氨基酸的鉴定。版权所有（C）2016 John Wiley＆Sons，Ltd.

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