engleski

Photodynamics of retinal chromophore-counterion pairs

The fundamental understanding of photochemical processes of complex biomolecular systems like retinal is only one piece of puzzle in understanding the Nature and one step closer to the construction of artificial biomimetic light driven photo-switches. Quantum-mechanical anharmonic frequency calculations confirmed the existence of two types of aggregates between protonated all-trans n- butylamine Schiff base of retinal (nSBR+) and the hydrogen bonded trifluoroacetic acid counterion. Using nonadiabatic dynamics simulations of the chromophore-counterion pairs in the dichloromethane, it is shown that the relaxation processes that set in after photo-excitation involve as a decisive step a formation of an inter-molecular charge transfer state via hole translocation from the retinal backbone to the counterion. In solution, this leads to dissociation of the chromophore-counterion pair and abortion of the photoisomerization, but constraining the distance of a counterion results in increasing biologically active C13=C14 bond length. Simulations of solvated nSBR+ reveal rotations around formally single bonds as a non- reactive channel.

interakcije kromofora s protuionom; vodikova veza; neadijabatska dinamika; retinal

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