LABORATORY
BIOMOLECULAR LAYERS
HEAD: Acad. Alexander G. Petrov, Dr. Sci.
tel: 8758 061; e-mail: agpetrov@issp.bas.bg
TOTAL STAFF: 6
RESEARCH SCIENTISTS: 6
Asist. Prof. S.Naydenova, Ph.D.
Asist. Prof. Y.Marinov, Ph.D.
Asist. Prof. L.Todorova
T.Angelov, chemist
M.Dencheva-Zarkova, technologist
RESEARCH ACTIVITIES:
Viscoelastic spectra of homeotropic nematic layers of MBBA oriented by self-assembled films
with different degree of desorbtion: high (dilauroyl phosphatidyl choline, DLPC) and low
(chromolan) have been studied by a phase-sensitive flexoelectric spectroscopy method.
Orientants desorb from the surface and dissolve in the nematic, producing a surface gradient
of concentration of the orientant. Extended theoretical treatment was implemented resulting
in spectral shapes, which have been successfully compared to the experiment, yielding
information about the surfactant gradient. These results permit us to reveal the existence
and the structure of a desorbed layer of orientant in homeotropic oriented nematics.
The linear electro-optic response of polymer dispersed liquid crystal films (PDLC) has been
studied under a.c. electric field exitation. Micrometer sized droplets of cyanobiphenyl
mixtures were formed in a Norland Optical Adhesive 65 photopolymer by
photopolymerization-induced phase separation and in polymethylmetacrylate by solvent induced
phase separation. Samples with various average nematic droplet size were systematically
investigated. The temperature dependence of the first harmonic electrooptic spectra was
obtained. Peculiar picks and double peaks in the spectra were found at temperatures close to
the clearing point, especially in samples with narrow distributions of droplet size.
A flexoelectric origin of the first harmonic spectra in confined nematic systems is discussed.
The effects of cadmium ions on ultrathin lipid bilayers of nanometer thickness and bilayers
containing alamethicin ion channels have been investigated. It was found that cadmium ions
increase the membrane stability against electroporation (electroformation of nanosized
conducting pores) and reduce the open probability of alamethicin channels.
PUBLICATIONS:
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A. G. Petrov, Mechanoelectric properties of BLMs, Chapter 6 in: Planar Lipid Bilayers
(BLMs) and their Applications. Eds. HT Tien and A. Ottova, Elsevier Science,
Amsterdam- NY, 2003, pp. 205-238.
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H. P. Hinov, I. Bivas, M. D. Mitov, K. Shoumarov, Y. Marinov, A further experimental
study of parallel surface - induced flexoelectric domains (PSIFED) (flexo - dielectric
walls), Liq. Cryst., 2003, 30, 1293 - 1317.
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S. Naydenova, A. Zheliaskova, R. Ugrinov, Y. Marinov, A.G.Petrov, Ion-channel
containing lipid membranes interacting with heavy metal ions, J.Mat.Sci.: Mat.
Electronics 14, 815-816 (2003)
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L.Todorova, T.Angelov, Y. Marinov, A.G.Petrov, Evidence of flexoelectricity in
polymer-dispersed liquid crystals, J.Mat.Sci.: Mat. Electronics 14, 817-818 (2003)
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G. Diankov, H. Naradikian, T. Angelov , Polymer stabilized liquid crystal indicator
used in the thermometry, J.Mat.Sci.: Mat. Electronics 14, 831-832 (2003)
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S.Naydenova, I.R.Mellor, A.G.Petrov, Effect of heavy metal ions on lipid bilayers
containing gramicidin channels, Compt. Rend. Acad. bulg. Sci. 56, No 3, 63-68 (2003)
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S. Naydenova, ΠΆ. Angelov, Y. Marinov, A.G. Petrov , Flexoelectric response in
polymer-liquid crystal lecithin system, Nanoscience & Nanotechnology,3, eds. E.
Balabanova, I. Dragieva, Heron Press, Sofia, 2003, p. 238 - 240
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G. Diankov, H. Naradikian, T. Angelov, R. Tomova, Optical properties of polymer
stabilized liquid crystal indicator - 1, Nanoscience & Nanotechnology,3, eds. E.
Balabanova, I. Dragieva, Heron Press, Sofia, 2003, p. 241 - 242
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A. G. Petrov, Present state of the generalized molecular asymmetry model in
liquid crystal physics, Bulg. J. Phys. 30, in press (2003)
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L. Todorova, S. Naydenova, T. Angelov, Y. Marinov, A.G. Petrov Flexoelectric study of
cyanobiphenil liquid crystals dispersed in various polymer matrixes, Bulg. J. Phys.
30, in press (2003)
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H. Naradikian, B. Katranchev, T. Angelov, R. Ugrinov, Optical properties in polymer
stabilized liquid crystal indicator used in the thermometry - 2, Bulg. J.Phys. 30, in
press (2003)
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Y. Sarov, T. Angelov and S. Sainov, Optical properties of polymer dispersed liquid
crystals, Bulg. J. Phys. 30, in press (2003)
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L. Todorova, Y. Marinov, I. Maslyanitsyin, S. Torgova, A.G. Petrov, Surface
dessipation in homeotropic nematic layers characterized by orientant desorption,
Bulg. J. Phys. 30, in press (2003)
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Y. Marinov, S. Naydenova, A. G. Petrov, Wedge-like asymmetry contribution to
flexoelectricity in nematic mixtures, Bulg. J. Phys. 30, in press (2003)
ONGOING RESEARCH PROJECTS:
Financed by the Bulgarian Academy of Sciences and by the Bulgarian National Council
"Scientific Studies", Project F-1003/00: "Opto-mechano-electricity in photoactive nano
liquid crystal systems".
COLLABORATION:
"Orientation ordered molecular nano structures for the optoelectronics" - Institute of
General Physics - Moscow, Joint Research Project between BAS and RAS, Russia
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