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Properties of Hybrid Complexes Composed of Photosynthetic Reaction Centers from the Purple Bacterium Rhodobacter sphaeroides and Quantum Dots in Lecithin Liposomes

V. E. Zagidullin1, E. P. Lukashev1*, P. P. Knox1, N. Kh. Seifullina1, O. S. Sokolova1, E. V. Pechnikova2, H. Lokstein3, and V. Z. Paschenko1

1Biology Faculty, Lomonosov Moscow State University, 119991 Moscow, Russia; fax: (495) 939-1115; E-mail: lukashev@biophys.msu.ru

2Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninsky pr. 59, 119333 Moscow, Russia; E-mail: eugenia.pechnikova@gmail.com

3Institute of Molecular, Cell and Systems Biology, Glasgow Biomedical Research Centre, 120 University Place, University of Glasgow, G12 8TA Glasgow, UK; E-mail: Heiko.Lokstein@glasgow.ac.uk

* To whom correspondence should be addressed.

Received May 22, 2014; Revision received June 23, 2014
Quantum dots (QDs) can absorb ultraviolet and long-wavelength light energy much more efficiently than natural light-harvesting proteins and transfer the excitation energy to photosynthetic reaction centers (RCs). Inclusion into liposomes of RC membrane pigment–protein complexes combined with QDs as antennae opens new opportunities for using such hybrid systems as a basis for artificial energy-transforming devices that potentially can operate with greater efficiency and stability than devices based only on biological components. RCs from Rhodobacter sphaeroides and QDs with fluorescence maximum at 530 nm (CdSe/ZnS with hydrophilic covering) were embedded in lecithin liposomes by extrusion of a solution of multilayer lipid vesicles through a polycarbonate membrane or by dialysis of lipids and proteins dispersed with excess detergent. The dimensions of the resulting hybrid systems were evaluated using dynamic light scattering and by transmission cryoelectron microscopy. The efficiency of RC and QD interaction within the liposomes was estimated using fluorescence excitation spectra of the photoactive bacteriochlorophyll of the RCs and by measuring the fluorescence decay kinetics of the QDs. The functional activity of the RCs in hybrid complexes was fully maintained, and their stability was even increased.
KEY WORDS: purple bacteria, photosynthetic reaction center, quantum dots, liposomes, energy transfer

DOI: 10.1134/S0006297914110054