Silver Nanoparticles Strongly Affect the Properties of Bacteriorhodopsin, a Photosensitive Protein of Halobacterium Salinarium Purple Membranes

Abstract

Interaction of silver nanoparticles (AgNPs) with purple membranes (PM) has been studied using atomic force microscopy and optical spectroscopy. It was shown that AgNPs alter the photocycle of the bacteriorhodopsin (BRh) molecules located in SERS-active spots. AgNPs suppresses the photocycle by “freezing” the state of retinal in which BRh has bound AgNPs. Outside SERS-active spots, BRh molecules retain the capacity for carrying out the photocycle but with shorter lifetimes of its photointermediate states. Thus, the AgNPs may affect the BRh photocycle through its acceleration in the regions of weak AgNPs-PM interaction or by the photocycle freezing in the SERS-active spots.