ИСТИНА

Voltage-dependent translocation of a series of cationic rhodamine B derivatives differing in alkyl chain length (ethyl, butyl, octyl, dodecyl, octadecyl) were studied on a planar bilayer phosphatidylcholine (PC) membrane. For this purpose, electrical current relaxation after a voltage jump was measured. For a given compound, the rate of translocation from one lipid monolayer to another increased in a following series of lipids: Diphytanyl-PC> Dioleyl-PC> Diphytanoyl-PC> Dierucoyl-PC. For every lipid studied, the translocation rate increased with the increase in the hydrocarbon chain length of the rhodamine derivatives. The increase was most pronounced for compounds having short alkyl chain. The increase was apparently related to the free energy gain of a transfer of the alkyl group from the polar surface into membrane center because of the presence of gradual polar profile on the membrane. Our results allowed us to estimate differences of the dipole potentials values of Dioleyl-PC, Diphytanoyl-PC and Dierucoyl-PC membranes compared to Diphytanyl-PC. These differences were 88, 106.5 and 120 mV, respectively.