Vol. 2 No. 1 March 1997

Volume 2 (1997) pp 3-7
Title CONTROLLED DRUG DELIVERY USING MAGNETOLIPOSOMES
Authors M. Babincova, P. Babinec
Abstract For targeted drug delivery a variety of protector or carrier systems has been developed. One of the promising approaches uses liposomes, which may be partially directed toward particular types of cells by means of antibodies or other ligands. We have proposed recently a new method for drug targeting based on magnetoliposomes, which are liposomes with subdomain magnetite (Fe3O4) particles with a diameter of (10 nm incorporated in their bilayers. Due to their magnetic sensitivity a non-homogenous magnetic field may be used for the targeting of magnetoliposomes to a given tissue. Because magnetite particles are strong microwave absorbers we have experimentally analyzed the influence of microwave radiation with a frequency of 2.45 GHz on the permeability of phosphatidylcholine magnetoliposomes. We have found for example that microwave radiation with specific absorbed power of 400 mW/g almost completely releases entrapped 6-carboxy-fluorescein in 15 min. The probable underlying mechanism is heating of Fe3O4 particles which leads to a perforation of lipid bilayers and subsequent leakage of entrapped magnetoliposome volume, so microwave radiation may be used for controllable release of drugs at low doses of microwave radiation intensities as compared with conventional microwave hyperthermia used previously by other authors.
Address and Contact Information Department of Biophysics and Chemical Physics, Comenius University, MFF UK, Mlynska dolina, 842 15 Bratislava, Slovakia
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 9-13
Title ERYTHROCYTES VESICULATE AT HIGH pH
Authors M. Bobrowska-Hagerstrand1, A. Iglic2, H. Hagerstrand1
Abstract Human erythrocytes were incubated at alkaline pH. In samples equilibrating within 60 min to pH 11 erythrocytes underwent prelytic vesiculation (fragmentation). Erythrocytes developed large (diameter often 1-2um) hemoglobin-filled blebs which could be released to the outer medium as hemoglobin containing vesicles. It is suggested that the described vesiculation at high pH occurs due to an uncoupling of the membrane skeleton from the lipid bilayer. Due to the uncoupling from the skeleton the erythrocyte lipid bilayer may behave similar to the membrane of a giant lipid vesicle.
Address and Contact Information 1Department of Biology, Abo Akademi University, FIN-20520, Abo/Turku, Finland
2Faculty of Electrical Engineering and Institute of Biophysics, University of Ljubljana, SI-1000, Ljubljana, Slovenia
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 15-24
Title ESTIMATION OF THE ORGANOTIN COMPOUNDS PARTITION INTO PHOSPHATIDYLCHOLINE BILAYERS WITH A pH SENSITIVE FLUORESCENCE PROBE
Authors M. Langner, H. Kleszczynska
Abstract The relative partition of trialkyltin and dialkyltin chlorides into the phosphatidylcholine membrane was estimated with a fluorescein dye attached to the phosphatidylethanolamine headgroup (Fluorescein-PE). Changes of pH in the vicinity of the membrane, caused by the adsorption of charged organotin compounds onto the surface, are measured with Fluorescein-PE. Measurements show that dialkyltin and trialkyltin chlorides at low concentrations (below 4 uM) adsorb onto the membrane surface in the charged form and that their relative partition depends on the length of the hydrocarbon residues. Tributyltin chloride was found to be the exception. Its effect on Fluorescein-PE fluorescence in the lipid bilayer was a complex dependence on its concentration in the sample, suggesting conformational changes in the lipid bilayer.
Address and Contact Information Department of Physics and Biophysics, Agricultural University, Norwida 25, 50-375 Wroclaw, Poland
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 25-29
Title COMPARISON OF THE INTERACTION OF DIPHENYLTIN AND TRIPHENYLTIN CHLORIDES WITH PHOSPHOLIPID BILAYERS
Authors B. Rozycka-Roszak, R. Zylka, S. Przestalski
Abstract The interaction of diphenyltin and triphenyltin chlorides with phospholipid bilayers was studied by means of 1H-NMR and differential scanning calorimetry. It is observed that diphenyltin chloride affects the phase transition of DPPC much more than triphenyltin chloride. The aromatic protons of both di- and triphenyltin chlorides give two 1H-NMR signals, which are shifted in the presence of lecithin.
Address and Contact Information Department of Physics and Biophysics, Agricultural University, Norwida 25, 50-375 Wroclaw, Poland
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 31-52
Title MOLECULAR APPROACHES TO LEAF GUARD CELLS
Authors B. Mueller-Roeber
Abstract Stomatal guard cells are highly differentiated cell types within the epidermis of higher plant leaves. These cells are intimately involved in regulating gas exchange, i.e. the release of water and the uptake of CO2, through the leaf surface. Guard cells represent an interesting cell type since they respond to various plant internal (e.g. hormones) and external (e.g. humidity, light, CO2) signals in a relatively simple manner. Stomatal pore size is changed by modulating the level of osmotically active compounds within the guard cells. In the past, guard cells have mainly been studied using electrophysiological, biochemical and whole-plant techniques. Only recently molecular techniques have been applied to address questions regarding control mechanisms of stomatal functioning. In the following a short overview is given on these molecular approaches.
Address and Contact Information Max-Planck-Institute of Molecular Plant Physiology, Karl-Liebknecht-Str. 25, Haus 20, D-14476 Golm/Potsdam, Germany
Tel.: +49-331-9772787; Fax: +49-331-9772301; E-mail: bernd@mpimpgolm.mpg.de
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 53-58
Title ESR STUDY OF MICELLIZATION PROCESS OF NNN-TRIMETHYLGLYCINETETRADECYL ESTER CHLORIDE
Authors M. Podolak1, D. Man1, S. Przestalski2
Abstract Formation of micelles of the fourteen-carbon amphiphilic ammonium salt ( N,N,N - trimethylglycinetetradecyl ester chloride - AS V-14 ), was studied using the ESR spin probe method. The probe used was 2-hexyl-2-[11-methoxy-11-oxoundecyl]-4,4-dimethyl-3oxazolidinyloxy [Met (5,10)]. The micelles formation process was signalized by changes in ESR spectra of a probe. The probe spectrum in aqueous environment has the shape of one broad line, whereas three narrow lines are observed in a hydrophobic environment. The study showed that the critical micellar concentration (CMC) of the AS V-14 compound amounts to about 1.7 mM. This agrees approximately with the value obtained from calorimetric measurements. After addition of oleic acid into the solution (by intensive shaking) it was found that AS V-14 micelles start to form at concentration of about 0.07 mM. The reduction in the CMC value may be caused by formation of mixed micelles, containing AS V-14 and fatty acid.
Address and Contact Information 1Opole University, Institute of Physics, Oleska 48, 45-052 Opole, Poland
2Department of Physics and Biophysics, Agricultural University, Norwida 25, 50-375 Wroclaw, Poland
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 59-68
Title PHOTO-OXIDATION OF CHLOROPHYLL A IN DIGALACTOSYL-DIACYLGLYCEROL LIPOSOMES CONTAINING XANTHOPHYLL PIGMENTS: INDICATION OF A SPECIAL PHOTOPROTECTIVE ABILITY OF ZEAXANTHIN
Authors J. Sielewiesiuk *, M. Matula and W. I. Gruszecki
Abstract Photoprotective efficiency of lutein, zeaxanthin and violaxanthin in liposomes made of digalactosyldiacylglycerol (DGDG) has been investigated. It was found that zeaxanthin is about ten times more effective than the two other xanthophylls in inhibition of chlorophyll a photo-oxidation. Kinetics of chlorophyll photobleaching suggests that exceptional photoprotective efficacy of zeaxanthin in membranes consists in effective scavenging of free radicals. High photoprotective efficiency of zeaxanthin in membranes correlates with its physiological function.
Address and Contact Information Department of Biophysics, Institute of Physics, Maria Curie-Sklodowska University, 20-031 Lublin, Poland
* corresponding author, Fax: +(48-81) 37-61-91
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp>69-76
Title ENDOGENOUS OSCILLATIONS OF THE TRANSCRIPT AMOUNTS OF SUBUNIT-c OF THE V-ATPASE OF MESEMBRYANTHEMUM CRYSTALLINUM WITH HARMONIC FREQUENCY RESONANCES UNDER CONTINUOUS ILLUMINATION
Authors B. Rockel1, B. Blasius2, F. Beck2, R. Ratajczak2, U. Luttge3
Abstract The amounts of mRNA of subunit-c (proteolipid) of the V-ATPase of mature leaves of Mesembryanthemum crystallinum L. in the state of C3-photosynthesis were analyzed for a time-series of 96 h under constant conditions in continuous light. Fourier-transform analysis of the data showed endogenous oscillations of the mRNA with period lengths of 48, 24 and 12 h, i.e. harmonic frequency resonances.
Address and Contact Information 1Max-Planck-Institut fur Biochemie, Am Klopferspitz 18a, D-82152 Martinsried, Germany
2Institut fur Kernphysik, Technische Hochschule Darmstadt, Schlosgartenstr. 9, D-64289 Darmstadt, Germany
3Institut fur Botanik, Technische Hochschule Darmstadt, Schnittspahnstr. 3-5, D-64287 Darmstadt, Germany
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 77-87
Title MODULATION OF 5-N-ALKYLRESORCINOL HEMOLYTIC PROPERTIES BY DIVALENT CATIONS. DEPENDENCE OF THE EFFECT OF CATIONS ON ALKYLRESORCINOL STRUCTURE
Authors M. Stasiuk and A. Kozubek
Abstract It was demonstrated that the process of hemolysis of erythrocytes induced by resorcinolic lipids is inhibited by divalent cations present in the incubation medium. The extent of inhibition is dependent on both type of the cation and hemolytic agent. The most susceptible upon the cation presence is the lysis induced by shortest (C15) and medium-chained (C19) 5-n-alkylresorcinols, those of the highest observed hemolytic potencies. Furthermore, the protection was the stronger the stronger lytic activity was excerted by studied compound. The homologs with longest side chain studied, although exhibiting the lowest hemolytic activity by themself were the least susceptible to inhibition of their hemolytic activity by cations. The effect of cobalt cation has been found to be intermediate between the effect of Mn2+ and Zn2+. The most effective in protection of erythrocytes was Zn2+ which almost completely protected the cells against alkylresorcinol-induced lysis already at the concentrations above 10-6 M.
Address and Contact Information Institute of Biochemistry, Wroclaw University, Przybyszewskiego 63/77, 51-148 Wroclaw, Poland
[Rozmiar: 1332 bajtów]

Volume 2 (1997) pp 89-100
Title PROPERTIES OF LIPID BILAYERS MODIFIED BY LONG-CHAIN POLYPRENOLS
Authors K. Walinska1, T. Janas2, T. Chojnacki3, E. Swiezewska3, T. Janas*1
Abstract It was demonstrated that tetracosaprenol ( C120 ) influences some properties of phosphatidylcholine (DOPC) macrovesicular bilayer lipid membranes. The membrane electric capacitance has been measured for different mixtures of tetracosaprenol and DOPC. The membrane thickness, the permeability coefficient for Na+ ions and membrane Young's modulus were determined. Values of the membrane Young's modulus and permeability coefficient for Na+ ions for different concentration of C120 in bilayers were compared with the same dependencies for hexadecaprenol (C80) and dotriacontaprenol (C160 ). Tetracoasaprenol slightly decreases membrane capacitance, increases membrane ionic permeability for sodium ions and membrane elastic deformability and slightly increases membrane hydrophobic thickness. The results also show that the length of a polyprenol chain modulate the influence of polyprenols on membrane Young's modulus and permeability coefficient for sodium ions. On the basic of the studies we suggest that long-chain polyprenols modify bilayer lipid membranes by the formation of fluid microdomains which modulate the membrane hydrophobic thickness.
Address and Contact Information 1Department of Biophysics, Institute of Biotechnology and Environmental Sciences, Pedagogical University, Al. Wojska Polskiego 69, 65-762 Zielona Gora, Poland.
2Biophysics Laboratory, Department of Physics, Technical University, Podgorna 50, 65-246 Zielona Gora, Poland.
3Department of Lipid Biochemistry, Institute of Biochemistry and Biophysics, Polish Academy of Sciences, A. Pawinskiego 5a, 02-106 Warszawa, Poland.
* corresponding author
[Rozmiar: 1332 bajtów]