We report a study of the primary photo-dissociation dynamics of aqueous alanine, isoleucine and proline by 200 nm UV pump-IR probe transient absorption spectroscopy. Photo-dissociation of the three amino acids predominantly results in decarboxylation, and 38 ± 7% of the excited alanine, 35 ± 10% of the excited isoleucine and 47 ± 10% of the excited proline zwitterions remain dissociated 100 picoseconds after the excitation. The decarboxylation occurs from a transient intermediate with a lifetime of ∼20 picoseconds to which we assign the excited state of the amino acids based on comparison of the measured and calculated IR spectra, and calculated excited state energy surfaces.

中文翻译：

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水溶液中氨基酸的主要光解离动力学：打破Cα键。

我们报告了对丙氨酸，异亮氨酸和脯氨酸水溶液的主要光解离动力学的研究，该动力学通过200 nm紫外泵浦IR探针瞬态吸收光谱法进行。这三个氨基酸的光离解主要导致脱羧，并且在激发后100皮秒保持离解的38±7％的丙氨酸，35±10％的异亮氨酸和47±10％的脯氨酸两性离子离解。脱羧发生在一个瞬态中间体上，该中间体的寿命约为20皮秒，我们根据测得的和计算出的IR光谱以及计算出的激发态能表面，将其分配为氨基酸的激发态。