Probing the rhodopsin cavity with reduced retinal models at the CASPT2//CASSCF/AMBER level of theory

J Am Chem Soc. 2003 Jun 11;125(23):6868-9. doi: 10.1021/ja035087d.

Abstract

We show that the ab initio CASPT2//CASSCF strategy previously used to investigate the ground and excited states of the chromophore of the vision receptor rhodopsin (Rh) in vacuo can be successfully implemented in a QM/MM scheme allowing for CASPT2//CASSCF/AMBER geometry optimization and excited state property evaluation in proteins. Two receptor models (Rh-1 and Rh-2) incorporating different reduced chromophores are investigated. It is shown that Rh-2 features a chromophore equilibrium structure with the correct helicity and a lambdamax that is only 52 nm blue-shifted from the observed value. This result should open the way to a qualitatively correct ab initio QM/MM modeling of the early excited state transient species involved in the vision process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Imidazoles
  • Models, Chemical
  • Models, Molecular
  • Protein Conformation
  • Purines
  • Quantum Theory
  • Retinaldehyde / chemistry*
  • Rhodopsin / chemistry*
  • Thermodynamics

Substances

  • 8-ethyl-4-methyl-2-phenyl-4,5,7,8-tetrahydro-1H-imidazo(2,1-i)purin-5-one
  • Imidazoles
  • Purines
  • Rhodopsin
  • Retinaldehyde