to CONTENTS

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:
  1. 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.
  2. 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.
  3. 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)
  4. 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)
  5. G. Diankov, H. Naradikian, T. Angelov , Polymer stabilized liquid crystal indicator used in the thermometry, J.Mat.Sci.: Mat. Electronics 14, 831-832 (2003)
  6. 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)
  7. 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
  8. 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
  9. A. G. Petrov, Present state of the generalized molecular asymmetry model in liquid crystal physics, Bulg. J. Phys. 30, in press (2003)
  10. 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)
  11. 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)
  12. Y. Sarov, T. Angelov and S. Sainov, Optical properties of polymer dispersed liquid crystals, Bulg. J. Phys. 30, in press (2003)
  13. 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)
  14. 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


Top

to CONTENTS