[Effect of R plasmid on cell membrane structure in Salmonella derby]. / Vliianie R-plazmidy na strukturu membran kletok Salmonella derby.

The structure of membranes of Salmonella derby cells both containing R-plasmid and free of plasmid was studied by small- and large-angle X-ray diffraction. Reflections with interplane distances of 8 and 11 A were detected, which are typical of plasmid-carrying S. derby cells. These reflections are assumed to be due to equidistant well ordered positions of the polar groups of phosphatidylcholine and phosphatidylethanolamine molecules on membrane surface. It is also suggested that the formation of these structures is determined by peculiar hydrophilic-hydrophobic interactions of the phospholipid in membranes.

[Effect of the external electrostatic field on the conformation of a macromolecule containing charged groups]. / Vliianie vneshnego élektrostaticheskogo polia na konformatsiiu makromolekuly, soderzhashchei zariazhennye gruppy.

A method for calculating the free energy of a macromolecule containing charged groups in electrostatic field in aqueous solution was proposed. The non-electrostatic component of free energy was calculated with consideration of van der Waals interactions between uncharged parts of the macromolecule. The electrostatic component of free energy was calculated with regard for the interactions of charged groups of the macromolecule with each other and with water molecules. It was found that, depending on the strength of external electric field, the free energy of the system passes through a minimum, whereas the internal energy passes through a maximum. By minimizing the free energy, relative changes in the mean radius 'r' and the distance between the termini of the macromolecule 'h' were calculated. It was found that, at some values of field strength, both 'r' and 'h' decrease. An increase in strength led to an increase in 'r' and 'h'. The regularities observed depend on the charge of the macromolecule and the spatial redistribution of macromolecules and counterions.

[Effect of the orientation of dipole fragments of the phospholipid molecule on the bilayer structure]. / Vliianie orientatsii dipol'nykh fragmentov molekul fosfolipida na strukturu bisloia.

By the method of minimization of phospholipid bilayers free energy it was shown that at a decrease of inclination angle of dipole fragments of phospholipid molecules to the bilayer surface there take place: a) an increase of bilayer density, b) a decrease of bilayer thickness caused by a decrease of dipole repulsive forces, c) an increase of the number of molecules in the bilayer due to hydrophobization of the latter. The existence of upper and lower critical angles of dipoles inclination to the bilayer surface were found: theta upcrit, theta lowcrit, if theta greater than or equal to the layers must be destroyed, and if theta less than or equal to theta lowcrit, transition of bilayers to the crystalline state must take place.