[Initiation of anion-selective ionic channels in bilayer membranes at lipid phase transitions]. / Vozniknovenie anion-selektivnykh ionnykh kanalov v bisloinykh membranakh pri fazovykh perekhodakh lipidov.

A study was carried out to electric parameters of single ionic channels initiated at phase transition of bromidmetilate 1,2-distearoyl-rac-glycero-3-(O-beta-dimethylaminoethyl)-methylphosphonate, whose molecules under conditions given below are possibly charged. It has been shown that changes of transmembrane current appear at phase transition temperature. Comparison between ionic selectivity of channels initiated at Tph.t in the membranes of DSL and its phosphate analog suggests that the channel walls initiated at phospholipid phase transitions are covered with polar groups of molecules.

The appearance of single-ion channels in unmodified lipid bilayer membranes at the phase transition temperature.

Ion-specific channels in artificial membranes have been formed by the addition of gramicidin A, alamethicin, polyene antibiotics and some proteins to the solution surrounding the bilayer lipid membrane. Until now there have been no reports of single-ion channels in unmodified lipid membranes. We have now studied the electrical conductance of planar lipid bilayers membranes made of synthetic distearoylphosphorylcholine (DSPC). Current fluctuations of amplitude approximately 1pA and duration approximately 1 s have been discovered at phase transition temperature, which shows that the appearance of ionic channels may be the result of lipid domain interactions. This would explain the dramatic increase in ion permeability observed in liposomes during phase transition. We suggest that these channels could conduct the transmembrane ionic current in biological membranes without the involvement of peptides and proteins.

[Free radicals formed during UV-irradiation of biological membrane lipids]. / Svobodnye radikaly, obrazuiushchiesia pri UF-obluchenii lipidov biologicheskikh membran.

Formation of free radicals under UV-irradiation of egg phosphatidyl choline, and synthetic phosphatidyl cholines and their analogs, as well as of their model compounds was studied. When saturated fat lipids are UV-irradiated radicals--CH2CH2 are accumulated at the expense of the breakage of--CH2CH2--COOH-bond. Radicals CH3--OCH2, HCO are formed in aminoalcohols due to the breakage of --OCH2--CH2N+(CH3)3- and--CH2--N+(CH3)3-bonds. It has been found that in natural and synthetic phospholipids radicals are formed in the course of photochemical reactions in complex ether and amine groups. The mechanism of radical formation is discussed.

[Ion permeability of bilayer membranes formed from synthetic phospholipids in the phase transition region]. / Ionnaia pronitsaemost' bisloinykh membran iz sinteticheskikh fosfolipidov v oblasti fazovogo perekhoda.

Ion permeability of black lipid membranes formed from synthetic phospholipids has been studied. The resistance of BLM formed from phosphatidylcholine, tiophosphatidylcholine, threealkylphosphate and threealkyltiophosphate was 10(7)--10(8) Ohm.cm2. It was shown that the membrane potential of the 10--30 mV arised in KCl gradient indicating the preference cation conductance in synthetic lipid membranes. A sharp decrease of the membrane conductance near to the phase transition temperature was discovered. The change of conductance by phase transition temperature was sensitive to chemical nature of the polar head of phospholipids used.

[Relationship between the surface properties of phosphoglycerides and the structure of the phosphorus part of the molecule]. / O zavisimosti poverkhnostnykh svoistv fosfoglitseridov ot stroeniia fosfornoi chasti molekuly

Comparative studies have been made on surface properties of phospholipids with different chemical composition and different structure of the hydrophylic moiety of the molecule. Substitution of phosphoroyl oxygen by sulfur, as in diacetyl lecithins, makes thiolecithin molecules in monolayer more compact. In case of an analogous substitution of oxygen by sulfur in phosphodiglycerides, packing of molecules in a monolayer remains unaffected. It may be suggested that this fact is associated with different position of hydrophobic radicals in the compounds investigated. In contrast to classic neutral and phosphorus-containing phosphoglycerides, diolphospholipids form more condensed monolayers. It was shown that alpha- and beta-phosphatidic acids with the same composition exhibit identical surface activity. Incorporation of hydrophobic groups of aromatic type into synthetic phospholipid analogues increases surface activity, the effect being dependent on the location of these groups with the molecule.