Fujihara Akimasa, Noguchi Naoki, Yamada Yuji, Ishikawa Haruki, Fuke Kiyokazu
Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
J Phys Chem A. 2009 Jul 23;113(29):8169-75. doi: 10.1021/jp902451k.
Photodissociation spectroscopy of solvated clusters of protonated tryptophan (TrpH(+)) and dipeptides containing tryptophan (Val-TrpH(+), Ala-TrpH(+), and Gly-TrpH(+)) has been carried out at low temperature to investigate the protonation and solvation effects on the electronic spectrum. For the protonated dipeptides, the S(1)-S(0) transition exhibits a substantial red shift due to the stronger interaction between the NH(3)(+) group and the indole pi ring. The S(1)-S(0) spectra of TrpH(+)(CH(3)OH)(n) clusters exhibit a drastic change with the number of methanol molecules. This behavior is interpreted in terms of the decrease in the interaction between the pi pi* and the repulsive pi sigma* states. Ala-TrpH(+) and Gly-TrpH(+) exhibit an extensive spectral change with addition of two methanol molecules. This change is ascribed to a conformational change, which is induced by the insertion of solvent molecule in between the NH(3)(+) group and the indole pi ring.
已在低温下对质子化色氨酸（TrpH(+)）以及含色氨酸的二肽（Val-TrpH(+)、Ala-TrpH(+)和Gly-TrpH(+)）的溶剂化簇进行了光解离光谱研究，以探究质子化和溶剂化对电子光谱的影响。对于质子化二肽，由于NH(3)(+)基团与吲哚π环之间更强的相互作用，S(1)-S(0)跃迁呈现出显著的红移。TrpH(+)(CH(3)OH)(n)簇的S(1)-S(0)光谱随甲醇分子数发生剧烈变化。这种行为可根据ππ与排斥性πσ态之间相互作用的减弱来解释。添加两个甲醇分子后，Ala-TrpH(+)和Gly-TrpH(+)呈现出广泛的光谱变化。这种变化归因于构象变化，该构象变化是由溶剂分子插入NH(3)(+)基团与吲哚π环之间所诱导的。
