Nguyen Doan Thuc, Fujihara Akimasa
Department of Chemistry, Graduate School of Science, Osaka Prefecture University, Osaka, 599-8531, Japan.
Orig Life Evol Biosph. 2018 Dec;48(4):395-406. doi: 10.1007/s11084-019-09574-9. Epub 2019 Apr 5.
Chiral recognition between tryptophan (Trp) and carbohydrates such as D-glucose (D-Glc), methyl-α-D-glucoside (D-glucoside), D-maltose, and D-cellobiose in cold gas-phase cluster ions was investigated as a model for chemical evolution in interstellar molecular clouds using a tandem mass spectrometer containing a cold ion trap. The photodissociation mass spectra of cold gas-phase clusters that contained Na, Trp enantiomers, and D-maltose showed that Na(D-Glc) was formed via the glycosidic bond cleavage of D-maltose from photoexcited homochiral Na(D-Trp)(D-maltose), while the dissociation did not occur in heterochiral Na(L-Trp)(D-maltose). The enantiomer-selective dissociation was also observed in the case of D-cellobiose. The enantiomer-selective glycosidic bond cleavage of disaccharides suggested that photoexcited D-Trp could prevent chemical evolution of sugar chains from D-enantiomer of carbohydrates in molecular clouds. The spectra of gas-phase clusters that contained Na, Trp enantiomers, and D-Glc indicated that enantiomer-selective protonation of L-Trp from D-Glc could induce enantiomeric excess via collision-activated dissociation of the protonated L-Trp. In the case of protonated clusters, photoexcited H(L-Trp) dissociated via C-C bond cleavage in the presence of D-Glc or D-glucoside, where the excited states of H(L-Trp) contributed to the enantiomer-selective reaction in the clusters. These enantiomer selectivities in cold gas-phase clusters indicated that chirality of a molecule induced enantiomeric excess of other molecules via enantiomer-selective reactions in molecular clouds.
使用包含冷离子阱的串联质谱仪，研究了色氨酸（Trp）与诸如D-葡萄糖（D-Glc）、甲基-α-D-葡萄糖苷（D-葡萄糖苷）、D-麦芽糖和D-纤维二糖等碳水化合物在冷气相团簇离子中的手性识别，以此作为星际分子云中化学演化的模型。含有Na、Trp对映体和D-麦芽糖的冷气相团簇的光解离质谱表明，Na(D-Glc)是通过光激发的同手性Na(D-Trp)(D-麦芽糖)中D-麦芽糖的糖苷键断裂形成的，而异手性的Na(L-Trp)(D-麦芽糖)则不发生解离。在D-纤维二糖的情况下也观察到了对映体选择性解离。二糖的对映体选择性糖苷键断裂表明，光激发的D-Trp可以阻止分子云中碳水化合物D-对映体糖链的化学演化。含有Na、Trp对映体和D-Glc的气相团簇的光谱表明，来自D-Glc的L-Trp的对映体选择性质子化可以通过质子化L-Trp的碰撞活化解离诱导对映体过量。在质子化团簇的情况下，光激发的H(L-Trp)在存在D-Glc或D-葡萄糖苷的情况下通过C-C键断裂解离，其中H(L-Trp)的激发态有助于团簇中的对映体选择性反应。冷气相团簇中的这些对映体选择性表明，分子的手性通过分子云中的对映体选择性反应诱导其他分子的对映体过量。
