In order to investigate chemical evolution in interstellar molecular clouds, enantiomer-selective photo-induced chemical reactions between an amino acid and disaccharides in the gas phase were examined using a tandem mass spectrometer containing an electrospray ionization source and a cold ion trap. Ultraviolet photodissociation mass spectra of cold gas-phase noncovalent complexes of protonated tryptophan (Trp) enantiomers with disaccharides consisting of two D-glucose units, such as D-maltose or D-cellobiose, were obtained by photoexcitation of the indole ring of Trp. NH2CHCOOH loss via cleavage of the Cα-Cβ bond in Trp induced by hydrogen atom transfer from the NH3+ group of a protonated Trp was observed in a noncovalent heterochiral H+(L-Trp)(D-maltose) complex. In contrast, a photo-induced chemical reaction forming the product ion with m/z 282 occurs in homochiral H+(D-Trp)(D-maltose). For D-cellobiose, both NH2CHCOOH elimination and the m/z 282 product ion were observed, and no enantiomer-selective phenomena occurred. The m/z 282 product ion indicates that the photo-induced C-glycosylation, which links D-glucose residues to the indole moiety of Trp via a C-C bond, can occur in cold gas-phase noncovalent complexes, and its enantiomer-selectivity depends on the structure of the disaccharide.

中文翻译：

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气相中质子化色氨酸与二糖的对映体选择性光诱导反应。

为了研究星际分子云中的化学演化，使用包含电喷雾电离源和冷离子阱的串联质谱仪检查了气相中氨基酸和二糖之间对映体选择性的光诱导化学反应。质子化色氨酸（Trp）对映异构体与由两个D-葡萄糖单元（例如D-麦芽糖或D-纤维二糖）组成的二糖的冷气相非共价复合物的紫外光解离质谱图是通过对Trp吲哚环进行光激发而获得的。在非共价杂手性H +（L-Trp）（D-麦芽糖）络合物中观察到由于氢原子从质子化的Trp的NH 3 +转移引起的Trp中Cα-Cβ键断裂引起的NH 2 CHCOOH损失。相比之下，在同手性H +（D-Trp）（D-麦芽糖）中发生与m / z 282形成产物离子的光诱导化学反应。对于D-纤维二糖，观察到NH 2 CHCOOH消除和m / z 282产物离子，并且没有发生对映异构体选择性现象。m / z 282产物离子表明，光诱导的C-糖基化（通过C键将D-葡萄糖残基连接到Trp的吲哚部分）可在冷气相非共价络合物中发生，其对映异构体选择性取决于在二糖的结构上。