Photoinduced modification of quantum dot optical properties affects bacteriorhodopsin photocycle in a (quantum dot)- bacteriorhodopsin hybrid material

A method for controlled changes in the radiative properties of quantum dots (QDs) in order to modulate the Forster resonance energy transfer (FRET) rate in nano-hybrid materials is proposed. The mechanism underlying the effect of QDs with optical properties modulated by UV laser irradiation on the photocycle of the photosensitive protein bacteriorhodopsin (bR) in its native purple membranes (PM) isolated from Halobacterium salinarum has been studied. The irradiation leads to a twofold decrease in the QD fluorescence quantum yield without changes in the extinction spectrum or the position or shape of the fluorescence spectrum. The bR photocycle is accelerated, which has been shown to be related to the changes of the surface potential of PM upon formation of their complexes with QDs