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I received my MSc in physics (1969) and PhD in physico-mathematical sciences (1976) both from the Lomonosov Moscow State University, Moscow, Soviet Union, and DSc degree in natural sciences (specialization in biophysics) in 1984 from the Jagiellonian University, Krakow, Poland. I received the title of professor of biological sciences (specialization in biophysics) from the President of Poland in 1995. Just after finishing the university I started to work in Biophysics Department, Institute of Molecular Biology at the Jagiellonian University as a teaching/research assistant, joined the faculty in 1977 and achieved the rank of professor in 1995. During 1988 – 1991 I was the Chairman of the Biophysics Department and from 1992 until 2000 the Head of the Laboratory of Structure and Dynamics of Biological Membranes. I directed 14 graduate students for their MSc degrees and supervised 4 students for their PhD degrees. I made my first visit to Milwaukee in 1980 and since that time have been at the National Biomedical EPR Center about 50% of the time. More than 40 of my papers have been co-authored with faculty or students from the EPR Center. In 2000 I emigrated to USA and joined the faculty of Medical College currently at the Associate Professor rank.
Over the last two decades, spin-label oximetry methods were developed and applied to study oxygen consumption and evolution in different biological and biochemical systems, as well as oxygen transport in better-defined model systems. I have been actively involved in the development and application of these methods. Although molecular oxygen is paramagnetic, the direct detection of oxygen in biological systems using the electron paramagnetic resonance (EPR) technique is not possible. However, indirect methods exist in which bimolecular collisions of oxygen with paramagnetic molecules alter the resonance characteristics of these probe paramagnetic molecules. Previously, the term "spin-label oximetry" described the application of nitroxide radical spin labels to oximetry measurements. This term should now be broadened to include other paramagnetic substances that are sensitive to collisions with oxygen, because new, stable free radicals and solid-state paramagnetic probes have been introduced, especially for in vivo oximerty measurements.In my investigations oxygen was also used as a probe to study three-dimensional molecular organization and dynamics in membranes. Finally, I would like to point out that because oxygen and nitric oxide (NO) are paramagnetic (oxygen has a triplet ground state, while NO has one unpaired electron making it a free radical), a similar approach can be used to study NO concentration and transport in biological and model systems. It has been shown that this method, called "spin-label NO-metry", is also quantitative giving a local NO diffusion-concentration product.
Over the last 25 years I have been investigating physical properties of lipid bilayer membranes. Using mainly the EPR spin-labeling method, we obtained unexpected results, which are significant for the better understanding of the function of biological membranes. These results can be summarized as follows: (1) Unsaturation of lipid alkyl chains greatly reduces the ordering and rigidifing effects of cholesterol, although, the unsaturation alone gives only minor fluidizing effects, as observed by order and reorientational motion, and rather significant rigidifing effects, as observed by translational motion of probe molecules; (2) Fluid-phase model membranes and cell plasma membranes are not barriers to oxygen and NO transport; (3) Polar carotenoids can regulate membrane fluidity in a way similar to cholesterol; (4) Formation of effective hydrophobic barriers to the permeation of small polar molecules across membranes requires alkyl chain unsaturation and/or the presence of cholesterol; (5) Fluid-phase micro-immiscibility takes place in cis-unsaturated phosphatidylcholine – cholesterol membranes and induces the formation of cholesterol-rich domains; (6) In membranes containing high concentration of transmembrane proteins a new lipid domain is formed, with lipid trapped within aggregates of proteins, in which the lipid dynamics is diminished to the level of gel- phase.
Presently my work is focused on the study of the formation of raft domains in model and biological membranes. The cell membrane has a 2-dimensional liquid-like structure, which contains domains of various time scale and space scale that are forming and dispersing continuously. Rafts are this type of membrane domains that require lipid interactions for their formation. The long-term objective of my study is to better understand the molecular mechanisms by which rafts form, are maintained and disintegrated in biological membranes. I am applying the pulse EPR spin labeling method "discrimination by oxygen transport" (DOT) for in situ studies of rafts in both model and cell membranes. This is a dual-probe saturation recovery EPR approach in which the observable parameter is the spin-lattice relaxation time of lipid spin labels and the measured value is the bimolecular collision rate between molecular oxygen and the nitroxide moiety of spin labels. The DOT method permits discrimination of different membrane domains because the collision rate between oxygen and the nitroxide moiety of spin labels (oxygen diffusion-concentration product) can be quite different in these domains. Additionally, membrane domains can be characterized by profiles of the oxygen diffusion-concentration product in situ without the need for separation.
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Collaborations:
Dr. Akihiro Kusumi, Department of Biological Sciences, Graduate School of Sciences, Nagoya University, Nagoya, Japan.
Dr. Marta Pasenkiewicz-Gierula, Biophysics Department, Institute of Molecular Biology, Jagiellonian University, Krakow, Poland.
Dr. Alexander N. Tikhonov, Department of Biophysics, Faculty of Physics, M.V. Lomonosov Moscow State University, Moscow, Russia.
Dr. Ronald N. McElhaney, Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.
Dr. Abbas Pezeshk, Department of Chemistry, Moorhead State University, Moorhead, Minnesota, USA.
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