Guo Tan, Geis Steve, Hedman Curtis, Arndt Michael, Krick William, Sonzogni William
Wisconsin State Laboratory of Hygiene, University of Wisconsin at Madison, Madison, Wisconsin 53718, USA.
J Am Soc Mass Spectrom. 2007 May;18(5):817-25. doi: 10.1016/j.jasms.2007.01.006. Epub 2007 Mar 2.
Beta-methylamino-L-alanine (BMAA) is a neurotoxic amino acid that can be produced by cyanobacteria in aqueous environments. To analyze this compound by gas chromatography/mass spectrometry (GC/MS), BMAA must be derivatized to a nonpolar, volatile compound. This can be accomplished by reacting BMAA with ethyl chloroformate. While carrying out electron ionization (EI) mass spectrometric analysis on the (13)C-labeled derivative, it was discovered that the formation of an ion with a peak at m/z 245.12 is the result of [CH(3)CH(2)O.] loss from the amino groups resulting from alpha-cleavage. This differs from previous reports that attributed this peak to alpha-cleavage of the carboxylic ester portion of the BMAA derivative. This finding is important for understanding BMAA derivative mass spectrometric fragmentation patterns and ultimately to properly identifying and quantifying BMAA. Fragmentation pathways for the formation of other major peaks observed in the EI mass spectra are also proposed.
β-甲基氨基-L-丙氨酸（BMAA）是一种神经毒性氨基酸，可由水环境中的蓝藻产生。要通过气相色谱/质谱联用仪（GC/MS）分析该化合物，BMAA必须衍生化为非极性挥发性化合物。这可以通过使BMAA与氯甲酸乙酯反应来实现。在对（13）C标记的衍生物进行电子电离（EI）质谱分析时，发现m/z 245.12处有峰的离子的形成是由于α-裂解导致氨基失去[CH(3)CH(2)O.]的结果。这与之前将该峰归因于BMAA衍生物羧酸酯部分α-裂解的报道不同。这一发现对于理解BMAA衍生物质谱碎裂模式以及最终正确鉴定和定量BMAA非常重要。还提出了在EI质谱中观察到的其他主要峰形成的碎裂途径。
