Ferré Nicolas, Olivucci Massimo
Dipartimento di Chimica, Università di Siena, via Aldo Moro I-53100 Siena, Italy.
J Am Chem Soc. 2003 Jun 11;125(23):6868-9. doi: 10.1021/ja035087d.
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.
我们表明，先前用于在真空中研究视觉受体视紫红质（Rh）发色团基态和激发态的从头算CASPT2//CASSCF策略可以成功地在QM/MM方案中实施，从而实现蛋白质中CASPT2//CASSCF/AMBER几何优化和激发态性质评估。研究了包含不同还原发色团的两种受体模型（Rh-1和Rh-2）。结果表明，Rh-2具有发色团平衡结构，其螺旋度正确，并且最大吸收波长仅比观测值蓝移52 nm。这一结果应为视觉过程中涉及的早期激发态瞬态物种的定性正确的从头算QM/MM建模开辟道路。
