210 ISSN 0030-400X, Optics and Spectroscopy, 2016, Vol. 121, No. 2, pp. 210–219. © Pleiades Publishing, Ltd., 2016. Original Russian Text © V.A. Oleinikov, K.E. Mochalov, D.O. Solovyeva, A.A. Chistyakov, E.P. Lukashev, I.R. Nabiev, 2016, published in Optika i Spektroskopiya, 2016, Vol. 121, No. 2, pp. 227–237. The Effect of Silver Nanoparticles on the Photocycle of Bacteriorhodopsin of Purple Membranes of Halobacterium salinarum V. A. Oleinikov a,b , K. E. Mochalov a,b , D. O. Solovyeva a,b , A. A. Chistyakov a,b , E. P. Lukashev c , and I. R. Nabiev b,d a Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, 117997 Russia b National Research Nuclear University, Moscow Engineering Physics Institute, Moscow, 115409 Russia c Moscow State University, Moscow, 119991 Russia d University of Reims Champagne-Ardenne, Reims, 51100 France e-mail: voleinik@mail.ru Received February 24, 2016 Abstract—The effect of silver nanoparticles (AgNPs) that are adsorbed on the surface of the purple mem- branes of Halobacterium salinarium bacteria on the optical properties and functional peculiarities of the light- sensitive protein bacteriorhodopsin (BR) has been demonstrated for the first time. Two mechanisms of the effect of AgNPs on the protein photocycle have been demonstrated using Raman scattering, giant Raman scattering, flash photolysis, and atomic force microscopy. It has been shown that the nanoparticles in the immediate spatial vicinity of BR fix its photocycle at the stage where it was at the moment of interaction with the nanoparticles. At greater distances, which reach three radii of an AgNPs, they have a weaker effect on BR, under which it retains the ability to be involved in the photocycle, however, has its parameters significantly changed. Thus, in the case of wild-type BR the photocycle accelerates and for the BR-D96N mutant it becomes slower. The data that are obtained could be of significance for creation of such optoelectronic hybrid systems with BR, where the parameters of its photocycle can be controlled using NPs. The results of the study may also be used in the field of nanobioengineering research, which is directed to creation of unique materials with controlled properties for recording and storage of information, energy transformation, and identification and characterization of trace amounts of analytes. DOI: 10.1134/S0030400X1608018X INTRODUCTION The resonance properties of nanoparticles (NPs) are actively used in modern sensor technologies for identification and investigation of the properties of biological objects [1]. One of the most promising directions in the development of these technologies is the use of giant Raman spectroscopy (GRS) for selec- tive detection and investigation of properties of single bacteria, viruses, and living cells [2–4]. One of the most popular systems that enhance Raman scattering (RS) is conventionally represented by sols of metal NPs. The enhancement of RS of the substance under study occurs in these systems due to its adsorption on the surface of NPs aggregates or due to formation of these aggregates on the surface of a spatially extended object such as bacteria. The Raman signal itself increases due to the enhancement of an electromag- netic field near the aggregates of metal NPs. The use of NPs of noble metals is preferable, since the frequen- cies of the surface plasmon resonance of spherical NPs are within the optical range. In particular, the reso- nance wavelength of spherical silver nanoparticles (AgNPs) is approximately 400 nm, while that of gold nanoparticles (AuNPs) is 550 nm. The position of the peak of the plasmon resonance is shifted to the long- wave region upon aggregation of NPs and/or change in their shape [5]. Moreover, nanoparticles are used for modulation of the function of light-sensitive proteins [6], e.g., bac- teriorhodopsin (BR). The possibility to tune the parameters of the resonance of NPs by changing their shape, size, and degree of aggregation makes it possi- ble to make hybrid nanosystems with resonance energy transfer that are based on conjugates of NPs and biological molecules. Examples of resonance interactions with biomolecules can be both plasmon interactions in a system of MeNPs and biomolecules and interaction with excitons in semiconductor NPs, quantum dots (QDs). In particular, the use of semi- conductor NPs in these systems makes it possible to broaden the spectral range of the natural protein func- tion, proton transfer, due to the energy transfer from a CONDENSED-MATTER SPECTROSCOPY