Charge localization and dynamics in rhodopsin

We present a Car-Parrinello ab initio molecular dynamics study of the retinylidene chromophore of rhodopsin, the membrane protein involved in the primary event in vision. We observe a coherent propagation of a conjugation defect associated with charge transport along the chromophore conjugated backbone. This solitonlike charge propagation is strongly coupled to the vibrational degrees of freedom due to the nonplanarity of the molecule. The implications for the chromophore isomerization mechanism are discussed.