Vékey K, Czira G
Central Research Institute for Chemistry, H-1025 Budapest, Pusztaszeri út 59-67, Hungary.
Anal Chem. 1997 May 1;69(9):1700-5. doi: 10.1021/ac960931m.
Mixtures of several amino acid pairs, in all four chiral combinations, were studied. The protonated trimers (A(2)BH(+)) fragment, forming ABH(+) and A(2)H(+) dimers. Abundance ratios of these fragments were measured in the mass-analyzed ion kinetic energy spectra of the trimers. These were found to depend on the stereochemistry (homo- or heterochiral form) of the ABH(+) dimer. The results were evaluated using the kinetic method, and the chiral discrimination was related to a difference in gas-phase basicity (GB) between the homo- and the heterochiral dimers. Four amino acid pairs (proline-tryptophan, phenylalanine-alanine, phenylalanine-proline, and phenylalanine-valine) were studied. Chiral discriminations were observed in all cases, relating to 0.4-4 kJ/mol differences in GB. The technique described here can generally be used to study enantiomers by mass spectrometry and is capable of reliably distinguishing energy differences as small as 0.2 kJ/mol in cluster ions.
研究了所有四种手性组合的几种氨基酸对的混合物。质子化三聚体（A(2)BH(+)）片段形成ABH(+)和A(2)H(+)二聚体。在三聚体的质量分析离子动能谱中测量了这些片段的丰度比。发现这些丰度比取决于ABH(+)二聚体的立体化学（同手性或异手性形式）。使用动力学方法对结果进行了评估，并且手性识别与同手性和异手性二聚体之间的气相碱度（GB）差异有关。研究了四对氨基酸（脯氨酸-色氨酸、苯丙氨酸-丙氨酸、苯丙氨酸-脯氨酸和苯丙氨酸-缬氨酸）。在所有情况下都观察到了手性识别，这与GB中0.4 - 4 kJ/mol的差异有关。这里描述的技术通常可用于通过质谱法研究对映体，并且能够可靠地区分簇离子中低至0.2 kJ/mol的能量差异。
