Microsolvation and protonation effects on geometric and electronic structures of tryptophan and tryptophan-containing dipeptides

J Phys Chem A. 2009 Jul 23;113(29):8169-75. doi: 10.1021/jp902451k.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Dipeptides / chemistry*
  • Electrons*
  • Models, Molecular
  • Protein Conformation
  • Protons*
  • Solvents / chemistry*
  • Spectrophotometry, Ultraviolet
  • Temperature
  • Tryptophan / chemistry*

Substances

  • Dipeptides
  • Protons
  • Solvents
  • Tryptophan