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Y S Tarahovsky

Publications and source records attributed to Y S Tarahovsky.

8 recordsLinked to original sources
PubMed2000

Electrostatic control of phospholipid polymorphism.

A regular progression of polymorphic phase behavior was observed for mixtures of the anionic phospholipid, cardiolipin, and the cationic phospholipid derivative, 1, 2-dioleoyl-sn-glycero-3-ethylphosphocholine. As revealed by freeze-fracture electron microscopy and small-angle x-ray diffraction, whereas the two lipids separately assume only lamellar phases, their mixtures exhibit a symmetrical (depending on charge ratio and not polarity) sequence of nonlamellar phases. The inverted hexagonal phase, H(II,) formed from equimolar mixtures of the two lipids, i.e., at net charge neutrality (charge ratio (CR((+/-))) = 1:1). When one type of lipid was in significant excess (CR((+/-)) = 2:1 or CR((+/-)) = 1:2), a bicontinuous cubic structure was observed. These cubic phases were very similar to those sometimes present in cellular organelles that contain cardiolipin. Increasing the excess of cationic or anionic charge to CR((+/-)) = 4:1 or CR((+/-)) = 1:4 led to the appearance of membrane bilayers with numerous interlamellar contacts, i.e., sponge structures. It is evident that interactions between cationic and anionic moieties can influence the packing of polar heads and hence control polymorphic phase transitions. The facile isothermal, polymorphic interconversion of these lipids may have important biological and technical implications.

Animals↗
PubMed2000

Study of F-actin interaction with planar and liposomal bilayer phospholipid membranes.

Interaction of the cytoskeletal protein F-actin with planar bilayer lipid membrane (BLM) induced formation of single ionic channels in both NaCl and KCl bathing solutions. We also recorded noiselike high-currentjumps with a mean conductivity of approximately 160 pS, which might represent the simultaneous opening and closing of several channels of lower conductivity. The ratio of cation to anion permeabilities (Pc/Pa) of the BLM with many channels in KCl was 26 +/- 2. Freeze-fracture electron microscopy revealed fibrillar-like structures on the hydrophobic surfaces of liposomal membranes. We also observed some structural features giving evidence for the penetration of F-actin fibers through an artificial phospholipid membrane. We suggest that the F-actin/lipids complexes can transmit electric signals in synaptic and other intercellular contacts.

Actins↗
PubMed1999

Physical and biological properties of cationic triesters of phosphatidylcholine.

The properties of a new class of phospholipids, alkyl phosphocholine triesters, are described. These compounds were prepared from phosphatidylcholines through substitution of the phosphate oxygen by reaction with alkyl trifluoromethylsulfonates. Their unusual behavior is ascribed to their net positive charge and absence of intermolecular hydrogen bonding. The O-ethyl, unsaturated derivatives hydrated to generate large, unilamellar liposomes. The phase transition temperature of the saturated derivatives is very similar to that of the precursor phosphatidylcholine and quite insensitive to ionic strength. The dissociation of single molecules from bilayers is unusually facile, as revealed by the surface activity of aqueous liposome dispersions. Vesicles of cationic phospholipids fused with vesicles of anionic lipids. Liquid crystalline cationic phospholipids such as 1, 2-dioleoyl-sn-glycero-3-ethylphosphocholine triflate formed normal lipid bilayers in aqueous phases that interacted with short, linear DNA and supercoiled plasmid DNA to form a sandwich-structured complex in which bilayers were separated by strands of DNA. DNA in a 1:1 (mol) complex with cationic lipid was shielded from the aqueous phase, but was released by neutralizing the cationic charge with anionic lipid. DNA-lipid complexes transfected DNA into cells very effectively. Transfection efficiency depended upon the form of the lipid dispersion used to generate DNA-lipid complexes; in the case of the O-ethyl derivative described here, large vesicle preparations in the liquid crystalline phase were most effective.

3T3 Cells↗
PubMed1998

Liposomes in gene therapy. Structural polymorphism of lipids and effectiveness of gene delivery.

The effective gene delivery to target cells is a basic challenge of gene therapy. In this review attention is focused on liposomal vehicles. They represent not only an alternative, but also an extension to the other methods of transfection where both biological and synthetic materials are utilized. The structural and phase transformations of lipids are generally inherent to nature and can be applied in practice. The liposomes could serve as a specific matrix for materials composed of proteins, polysaccharides, and various synthetic polymers. The investigation of structural polymorphism of lipids and DNA--lipid complexes is important for designing of effective carriers of genes and drugs.

Adenoviridae↗
PubMed1998

Structural organization and phase behavior of DNA-calcium-dipalmitoylphosphatidylcholine complex.

Freeze-fracture study of ultrastructure of DNA--calcium--dipalmitoylphosphatidylcholine (DPPC) complex was carried out at different temperatures. For high-speed cryofixation from controllable initial temperatures, a special thermostatic chamber was designed. The fracture surface of the complex was found to be considerably different from the initial DPPC liposomes: 1) the period of ripple phase was 25 nm in contrast to 15 nm for control samples; 2) the ripple phase was observed at temperatures ranging from 6 degreesC to lipid melting temperature; 3) at temperature above the lipid melting unordered worm-like folds were formed on the fracture surface. Their length was correlated with the length of DNA fragments used in the experiment. We suppose that DNA molecules adsorbed on the membrane surface were segregated to clusters, resulting in formation of a new phase with specific structure and properties.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1995

Structural changes in Escherichia coli membranes induced by bacteriophage T4 at different temperatures.

This paper presents some further evidence for our model of DNA translocation into Escherichia coli cells by bacteriophage T4 (see Tarahovsky, Y. S., Khusainov, A. A., Deev, A. A., Kim, Y. V. 1991. FEBS Lett. 289:18-22). When lowering the temperature, we succeeded in slowing down the infection process and in observing a few separate stages by electron microscopy. Also, potassium leakage at different temperatures was measured. At 0-6 degrees C the phage was found to be irreversibly adsorbed on the cell surface, its tail to be contracted, and the outer membrane to be invaginated. Membrane fusion and formation of broad intermembrane bridges with a hole for potassium leakage were shown to start above 7 degrees C. At about 17-20 degrees C the diameter of the bridge decreased considerably, which could correspond to the sealing of the membrane.

Adsorption↗
PubMed1994

Lysis of Escherichia coli cells induced by bacteriophage T4.

Structural changes in the envelope of Escherichia coli cells accompanying their lysis from without by bacteriophage T4 have been studied. The hypothesis concerning the role of collapse of membrane potential and formation of periplasmic vesicles in the process of lysis from without has been advanced.

Bacteriolysis↗