title: Probing the Photodynamics of Rhodopsins with Reduced Retinal Chromophores.
abstract: While the light-induced population dynamics of different photoresponsive proteins has been investigated spectroscopically, systematic computational studies have not yet been possible due to the phenomenally high cost of suitable high level quantum chemical methods and the need of propagating hundreds, if not thousands, of nonadiabatic trajectories. Here we explore the possibility of studying the photodynamics of rhodopsins by constructing and investigating quantum mechanics/molecular mechanics (QM/MM) models featuring reduced retinal chromophores. In order to do so we use the sensory rhodopsin found in the cyanobacterium Anabaena PCC7120 (ASR) as a benchmark system. We find that the basic mechanistic features associated with the excited state dynamics of ASR QM/MM models are reproduced using models incorporating a minimal (i.e., three double-bond) chromophore. Furthermore, we show that ensembles of nonadiabatic ASR trajectories computed using the same abridged models replicate, at both the CASPT2 and CASSCF levels of theory, the trends in spectroscopy and lifetimes estimated using unabridged models and observed experimentally at room temperature. We conclude that a further expansion of these studies may lead to low-cost QM/MM rhodopsin models that may be used as effective tools in high-throughput in silico mutant screening.
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.
authors.forename: Madushanka
authors.initials: M
authors.lastname: Manathunga
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.
authors.forename: Xuchun
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.
authors.forename: Hoi Ling
authors.initials: HL
authors.lastname: Luk
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.
authors.forename: Samer
authors.initials: S
authors.lastname: Gozem
authors.affiliation: Departamento de Química Física, Universidad de Alcalá , E-28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Luis Manuel
authors.initials: LM
authors.lastname: Frutos
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena , via A. Moro 2, I-53100 Siena, Siena, Italy.|Departamento de Química Física, Universidad de Alcalá , E-28871 Alcalá de Henares, Madrid, Spain.
authors.forename: Alessio
authors.initials: A
authors.lastname: Valentini
authors.affiliation: Aix-Marseille Université, CNRS, Institut de Chimie Radicalaire, 13397 Marseille, Cedex 20, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferrè
authors.affiliation: Department of Chemistry, Bowling Green State University , Bowling Green, Ohio 43403, United States.|Dipartimento di Biotecnologie, Chimica e Farmacia, Università di Siena , via A. Moro 2, I-53100 Siena, Siena, Italy.|University of Strasbourg Institute for Advanced Studies, 5, allée du Général Rouvillois, F-67083 Strasbourg, France.
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
mesh_terms: D017033:Anabaena / Q000378:metabolism; D007536:Isomerism; D008958:Models, Molecular; D011789:Quantum Theory; D012172:Retinaldehyde / Q000737:chemistry*; D012243:Rhodopsin / Q000737:chemistry*; D013696:Temperature
chemical_list: D012243:Rhodopsin; D012172:Retinaldehyde