The principal result obtained in the group of Dr. A.Kaulen and in the Laboratory of electrogenic processes (Dr. A.Semenov and co-workers) is the development of the direct electrometric technique which allows to monitor with high time resolution the partial stages of generation and decay of the transmembrane electric potential difference by the membrane proteins functioning as generators of electric current in the coupling biomembranes.

By means of this high-sensitive technique the electrical activities of bacteriorhodopsin from halobacteria, as well as cytochrome c oxidase, transhydrogenase, H+ ATPase from mitochondria, inorganic pyrophosphatase, cytochrome bc1-complex and reaction centers from the photosynthetic bacteria, photosystems I and II from cyanobacteria were directly demonstrated. These results proved to be an important experimental evidence for the chemiosmotic theory of the coupling of oxidation and phosphorylation in biological membranes, proposed by P. Mitchell.

The application of the direct electrometrical method for investigation of electrogenic reactions in pigment-protein complexes with point mutations of the functionally important amino acid residues in combination with the known three-dimensional crystal structure of these complexes allowed to learn the details of intraprotein electron and proton transfer mechanisms.

Investigation of the pecularities of the transmembrane charge transfer using inhibitor analysis, flash-spectrometry, studying of the temperature and pH-dependencies, redox-potentiometry and some other methods allowed to identify the nature of the definite electrogenic reactions as well as chemical groups providing the electrical potential difference formation by pigment-protein complexes in biomembranes.

The task of the Laboratory of hemoproteins (Dr. A. Arutynyan and co-workers) is to investigate the hemoptoteins using natural (CD) and magnetic (MCD) circular dichroism methods. A unique complex of equipment and software for investigation and deconvolution of the CD and MCD spectra were developed. The study of the multiheme proteins, such as cytochrome bc1-complexes, cytochrome oxidase, cytochrome bd and others were performed by these techniques. In addition, the Laboratory is engaged into scientific-methodological works which make available the above mentioned methods for all Institute members.

1. Semenov, A.Yu. Electrogenic steps during electron transfer via the cytochrome bc-complex of Rhodobacter sphaeroides chromatophores. FEBS Letters (1993) 321, 1-5.

2. Holz M., Drachev L.A., Mogi T., Otto H., Kaulen A.D., Heyn M.P., Skulachev V.P., Khorana H.G. Replacement of aspartic acid-96 by asparagine in bacteriorhodopsin slows both the decay of the M intermediate and the associated proton movement. Proc.Natl.Acad.Sci. USA (1989) .86, .2167-2171.

3. Konstantinov, A.A., Siletsky, S., Mitchell, D., Kaulen, A., Gennis, R.B. The roles of the two proton input channels in cytochrome c oxidase from Rhodobacter sphaeroides probed by the effects of site-directed mutations on time-resolved electrogenic intraprotein proton transfer. Proc. Natl. Acad. Sci. USA (1997), .94, .9085-9090.

4. Kalaidzidis, I.V., Kaulen, A.D. Cl-dependent photovoltage responses of bacterirhodopsin: comparison of the D85T and D85S mutants and wild-type acid purple form. FEBS Letters (1997) 418, 239-242.

5. Vassiliev, I.R., Jung, Y.-S., Mamedov, M.D., Semenov, A.Yu., Golbeck, J.H. Near-IR absorbance changes and electrogenic reactions in the microsecond-to-second time domain in photosystem I. Biophys. J. (1997) 72, 301-315.