Study of a Bacteriorhodopsin/TiO Hybrid System at the Molecular Level.

Bacteriorhodopsin (bR) is a light-harvesting membrane protein that represents a promising sensitizer of TiO for photovoltaic and photoelectrochemical devices. However, despite numerous experimental studies, the molecular-level understanding of the bR/TiO hybrid system is still unsatisfactory. In this contribution, we report the construction and analysis of an atomistic model of such a system. To do so, both steered molecular dynamics-molecular dynamics and quantum mechanics/molecular mechanics computations are applied to four different bR orientations on the anatase TiO surface. The resulting bR/TiO models are then used to compute the light absorption maxima changes relative to those of bR. We show that all four models reproduce the experimentally observed blue-shift value induced by bR binding on TiO and could be used to study the binding and binding-induced protein modifications. We conclude that the constructed models could provide a basis for future studies aiming to simulate the complex long-range electron transfer mechanism in bR/TiO-based solar energy conversion devices as well as in engineering bR to achieve enhanced efficiencies.