Effect of the phase state of the lipid bilayer on the structure and characteristics of the polycation-(anionic liposome) complex

Interaction of the cationic polymer poly-N-ethyl-4-vinylpyridinium bromide with bilayer vesicles (liposomes) composed of zwitterionic dipalmitoylphosphatidylcholine and anionic cardiolipin (the molar fraction of the negatively charged cardiolipin groups is 0.2) is studied. The composition and characteristics of the polycation-liposome complex are shown to be controlled by the phase state of the lipid membrane. Liposomes whose membranes exist in their LC state (“liquid” liposomes) keep their integrity in the complex with polycation. The adsorbed polycation can be completely removed from the liposomal membrane by the addition excess amounts of a competing polyanion. The adsorption of polycation on the surface of liposomes whose membranes exist the gel state (“solid” liposomes) leads to the formation of defects in the membrane, and the polycation’s adsorption with such liposomes becomes irreversible. The defects that form are also preserved when solid liposomes on whose surface the polycation is sorbed are transformed into the liquid state. Moreover, the reversible contact between polycation and liquid liposomes becomes irreversible once the liposomal membranes bound to the polycation transform into the solid state.     

Migration of a cationic polymer between lipid vesicles

The adsorption of a synthetic polycation, poly(N-ethyl-4-vinylpyridinium bromide) (PEVP), on the surface of bilayer lipid vesicles (liposomes) and the migration of adsorbed macromolecules between the liposomes are studied. Liposomes of three types are used, including (1) traditional two-component liposomes composed of neutral phosphatidylcholine (PC) and anionic cardiolipin (CL); (2) three-component liposomes consisting of PC, CL, and cationic dicetyldimethylammonium bromide (DCMAB); and (3) anionic PC/CL liposomes with a nonionic surfactant, poly(ethylene oxide)-cetyl alcohol ether (Briij 58), incorporated into their bilayers. The adsorption of PEVP on the surface of PC/CL liposomes is accompanied by their aggregation. Using the fluorescence method, it is shown that the units (segments) of the polycation undergo partial redistribution between the liposomes inside the aggregates formed from PC/CL liposomes (with and without a fluorescent label) and PEVP. On the contrary, three-component PC/CL/DCMAB and PC/CL/Briij liposomes are not aggregated, even with the complete neutralization of their charges by adsorbed PEVP. In both cases, the migration of PEVP molecules between individual (nonaggregated) liposomes is observed. Possible reasons for the aggregative stability of the three-component PC/CL/DCMAB and PC/CL/Briij liposomes and the mechanism of interliposome migration of PEVP in such systems are discussed.     

Joint action of antioxidants of phenol type and superoxide anion in the oxidation reactions

Initiated oxidation of cumene with oxygen in the presence of various phenol antioxidants and a supramolecular system containing the oxygen radical anion of was studied. It is shown that superoxide anion and ionol, hydroquinone, and ethyl gallate are the antagonists in the process of inhibition of the radical chain oxidation. Simultaneous introduction of the ascorbic acid and the radical anion of oxygen caused the synergistic effect.     

A study of the effect of metal corrosion inhibitors on the hydrogenation of steel and changes in its plasticity upon etching in sulfuric acid solutions

Effect of metal corrosion inhibitors, N-acetylmethylpyridium salts, on the hydrogen charging of 08 KP steel and changes in its plasticity upon its etching in solutions of 3 M sulfuric acid. Inhibitors more strongly diminishing the fraction of hydrogen atoms diffusing into the steel and preserving or raising its plasticity as compared with the shipment level were found.     

Free vibrations of axially polarized piezoceramic hollow cylinders of finite length

The problem of the free axisymmetric vibrations of longitudinally polarized piezoceramic hollow cylinders is solved by a numerical analytic method. The spline-collocation method with respect to the longitudinal coordinate is used to reduce the original problem of electroelasticity to an eigenvalue boundary-value problem for ordinary differential equations with respect to the radial coordinate. This problem is solved by the stable discrete-orthogonalization and incremental search methods. Numerical results are presented and the natural frequencies of the cylinders are analyzed for a wide range of their geometric characteristics     

The influence of additives to the Speier catalyst on hydrosilylation of functionalized alkenes

Hydrosilylation of several unsaturated compounds with triethoxysilane in the presence of the Speier catalyst with various additives influencing the reaction rate and selectivity was studied. The mechanism of hydrosilylation is discussed. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1413–1417, July, 1998.     

Structure of the frequency spectrum of nonaxisymmetric vibrations of a transversally isotropic hollow ball

We consider nonaxisymmetric vibrations of a hollow sphere made of a spherically Isotropic material. The original boundary-value problem is reduced to a system of ordinary differential equations by introducing new unknown junctions and expanding the sought solution in a series in spherical functions. The nonaxisymmetric problem of vibrations of a hollow ball decomposes into two independent problems that describe modes of first and second kind. The frequency spectrum for modes of first and second kind is analyzed.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 59, pp. 32–35, 1986.     

Numerical analysis of axisymmetric oscillations of an orthotropic cylindrical shell

The frequency spectrum of shells is analyzed by numerical methods using three-dimensional and applied theories. The axisymmetric oscillations of an orthotropic cylindrical shell with Navier conditions on the edges are investigated. The effect of boundary conditions on the frequency spectrum is also studied numerically.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 55, pp. 106–109, 1985.     

Vircator with ballistic focusing of an electron beam

A high-power microwave oscillator (vircator) is built around an ironless induction linac. The feature of this device is ballistic focusing of an electron beam in a diode-type system with a concentric spherical cathode and anode. The possibility of the vircator to generate high-power microwave pulses is demonstrated.