We demonstrate that a "brute force" quantum chemical calculation based on an ab initio multiconfigurational second order perturbation theory approach implemented in a quantum mechanics/molecular mechanics strategy can be applied to the investigation of the excited state of the visual pigment rhodopsin (Rh) with a computational error <5 kcal.mol(-1). As a consequence, the simulation of the absorption and fluorescence of Rh and its retinal chromophore in solution allows for a nearly quantitative analysis of the factors determining the properties of the protein environment. More specifically, we demonstrate that the Rh environment is more similar to the "gas phase" than to the solution environment and that the so-called "opsin shift" originates from the inability of the solvent to effectively "shield" the chromophore from its counterion. The same strategy is used to investigate three transient structures involved in the photoisomerization of Rh under the assumption that the protein cavity does not change shape during the reaction. Accordingly, the analysis of the initially relaxed excited-state structure, the conical intersection driving the excited-state decay, and the primary isolable bathorhodopsin intermediate supports a mechanism where the photoisomerization coordinate involves a "motion" reminiscent of the so-called bicycle-pedal reaction coordinate. Most importantly, it is shown that the mechanism of the approximately 30 kcal.mol(-1) photon energy storage observed for Rh is not consistent with a model based exclusively on the change of the electrostatic interaction of the chromophore with the protein/counterion environment.

T., A., N., F., & Olivucci, M. (2004). Structure, initial excited-state relaxation, and energy storage of rhodopsin resolved at the multiconfigurational perturbation theory level. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 101(52), 17908-17913 [10.1073/pnas.0407997101].

Structure, initial excited-state relaxation, and energy storage of rhodopsin resolved at the multiconfigurational perturbation theory level

OLIVUCCI, MASSIMO
2004

Abstract

We demonstrate that a "brute force" quantum chemical calculation based on an ab initio multiconfigurational second order perturbation theory approach implemented in a quantum mechanics/molecular mechanics strategy can be applied to the investigation of the excited state of the visual pigment rhodopsin (Rh) with a computational error <5 kcal.mol(-1). As a consequence, the simulation of the absorption and fluorescence of Rh and its retinal chromophore in solution allows for a nearly quantitative analysis of the factors determining the properties of the protein environment. More specifically, we demonstrate that the Rh environment is more similar to the "gas phase" than to the solution environment and that the so-called "opsin shift" originates from the inability of the solvent to effectively "shield" the chromophore from its counterion. The same strategy is used to investigate three transient structures involved in the photoisomerization of Rh under the assumption that the protein cavity does not change shape during the reaction. Accordingly, the analysis of the initially relaxed excited-state structure, the conical intersection driving the excited-state decay, and the primary isolable bathorhodopsin intermediate supports a mechanism where the photoisomerization coordinate involves a "motion" reminiscent of the so-called bicycle-pedal reaction coordinate. Most importantly, it is shown that the mechanism of the approximately 30 kcal.mol(-1) photon energy storage observed for Rh is not consistent with a model based exclusively on the change of the electrostatic interaction of the chromophore with the protein/counterion environment.
T., A., N., F., & Olivucci, M. (2004). Structure, initial excited-state relaxation, and energy storage of rhodopsin resolved at the multiconfigurational perturbation theory level. PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 101(52), 17908-17913 [10.1073/pnas.0407997101].
File in questo prodotto:
File Dimensione Formato  
Andruniów Proceedings of the National Academy of S.pdf

non disponibili

Tipologia: Post-print
Licenza: NON PUBBLICO - Accesso privato/ristretto
Dimensione 435.33 kB
Formato Adobe PDF
435.33 kB Adobe PDF   Visualizza/Apri   Richiedi una copia

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11365/24580
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo