title: The ultrafast photoisomerizations of rhodopsin and bathorhodopsin are modulated by bond length alternation and HOOP driven electronic effects.
abstract: Rhodopsin (Rh) and bathorhodopsin (bathoRh) quantum-mechanics/molecular-mechanics models based on ab initio multiconfigurational wave functions are employed to look at the light induced π-bond breaking and reconstitution occurring during the Rh → bathoRh and bathoRh → Rh isomerizations. More specifically, semiclassical trajectory computations are used to compare the excited (S(1)) and ground (S(0)) state dynamics characterizing the opposite steps of the Rh/bathoRh photochromic cycle during the first 200 fs following photoexcitation. We show that the information contained in these data provide an unprecedented insight into the sub-picosecond π-bond reconstitution process which is at the basis of the reactivity of the protein embedded 11-cis and all-trans retinal chromophores. More specifically, the data point to the phase and amplitude of the skeletal bond length alternation stretching mode as the key factor switching the chromophore to a bonding state. It is also confirmed/found that the phase and amplitude of the hydrogen-out-of-plane mode controls the stereochemical outcome of the forward and reverse photoisomerizations.
authors.affiliation: Chemistry Department, Bowling Green State University, Bowling Green, Ohio 43403, United States.
authors.forename: Igor
authors.initials: I
authors.lastname: Schapiro
authors.forename: Mikhail Nikolaevich
authors.initials: MN
authors.lastname: Ryazantsev
authors.forename: Luis Manuel
authors.initials: LM
authors.lastname: Frutos
authors.forename: Nicolas
authors.initials: N
authors.lastname: Ferré
authors.forename: Roland
authors.initials: R
authors.lastname: Lindh
authors.forename: Massimo
authors.initials: M
authors.lastname: Olivucci
mesh_terms: D004583:Electrons; D007536:Isomerism; D008027:Light; D055668:Photochemical Processes; D011487:Protein Conformation; D011789:Quantum Theory; D012243:Rhodopsin / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: C015017:bathorhodopsin; D012243:Rhodopsin