Microsolvation and protonation effects on geometric and electronic structures of tryptophan and tryptophan-containing dipeptides.
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.
Fujihara
Akimasa
A
Department of Chemistry, Graduate School of Science, Kobe University, Rokkodai, Nada-ku, Kobe 657-8501, Japan.
Noguchi
Naoki
N
Yamada
Yuji
Y
Ishikawa
Haruki
H
Fuke
Kiyokazu
K
D004151:Dipeptides / Q000737:chemistry*; D004583:Electrons; D008958:Models, Molecular; D011487:Protein Conformation; D011522:Protons; D012997:Solvents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014364:Tryptophan / Q000737:chemistry*
D004151:Dipeptides; D011522:Protons; D012997:Solvents; D014364:Tryptophan