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V V Chupin

Publications and source records attributed to V V Chupin.

13 recordsLinked to original sources
PubMed2000

2H-NMR comparative study of phosphocholine group conformation in bilayers composed of diacyl and dialkyl phosphatidylcholines.

Model membranes formed from 1,2-dihexadecyl-, 1,2-dipalmitoyl-, 1,2-ditetradecyl- or 1,2-dimyristoyl-rac-glycero-3-phosphocholine, deuterium-labelled at choline groups, in an excess of water were compared using 2H-NMR spectroscopy. The dynamics and conformation of the labelled choline segments were estimated based on spin-lattice relaxation time and residual quadrupole splittings. The trimethylammonium group of dialkyl phosphatidylcholine was shown to be more distant from the bilayer surface as compared with that of the diacyl analogues.

Biophysical Phenomena↗
PubMed1999

[Lipid inhibitors of phospholipase A2].

Results of studies of lipid inhibitors of phospholipase A2 are reviewed with a special emphasis on substrate specificity, special features of interfacial catalysis, and methods for the determination of the enzyme activity. The biological function of intracellular phospholipases is considered, and the possible use of inhibitors of a lipid nature for the modulation of the enzyme activity in pathological states of the human organism is discussed.

Enzyme Inhibitors↗
PubMed1996

On the synthesis of platelet-activating factor via acetylation of 1-alkyl-sn-glycero-3-phosphocholine. Formation of structural isomer of PAF in the presence of bases.

It has been shown that platelet-activating factor (PAF) specimens prepared via acetylation of 1-alkyl-sn-glycero-3-phosphocholine (lyso-PF) with acetic anhydride are heterogeneous. The contaminated compound was isolated and identified to be the structural isomer of PAF, 1-alkyl-3-acetyl-sn-glycero-2-phosphocholine (iso-PAF). It appeared, that iso-PAF is formed when performing the reaction in the presence of organic bases,but not under acid catalysis. The mechanism of iso-PAF formation is discussed.

Acetylation↗
PubMed1994

Regulation of lipid polymorphism is essential for the viability of phosphatidylethanolamine-deficient Escherichia coli cells.

Escherichia coli strain AD93 is unable to synthesize the nonbilayer lipid phosphatidylethanolamine and requires high concentrations of specific divalent cations for growth. Previous studies suggested that in this strain, cardiolipin in combination with divalent cations functionally replaces phosphatidylethanolamine, reflecting polymorphic regulation of membrane lipid composition. However, it is also possible that divalent cations are required for regulation of lipid packing or membrane surface potential. 2H NMR was employed to measure the effect of different divalent cations on lipid packing in aqueous dispersions of lipid extracts isolated from AD93 and the wild type parental strain W3899, which were grown with [11,11-2H2]oleic acid. The results indicate that a range of acyl chain order is compatible with growth and that Ba2+, which cannot support growth of AD93, can increase chain packing to the wild type level. By means of microelectrophoresis, it was shown that the growth-promoting cations and Ba2+ have a strong and comparable ability to screen the surface charge of large unilamellar vesicles prepared from AD93 lipid extracts. Therefore, it is unlikely that the growth-promoting capacity of divalent cations is primarily due to their effect on lipid packing or their potency to decrease the surface potential. Furthermore, the addition of small amounts of Ba2+ to a AD93 lipid dispersion with excess Mg2+ diminished HII phase formation. This observation can explain the growth arrest in AD93 cultures upon the addition of Ba2+ and further supports the conclusion that the cation requirement of this strain arises mainly from polymorphic regulation of lipid composition.

Barium↗
PubMed1993

[Formation of a structural isomer of platelet activating factor during acetylation of 1-alkyl-sn-glycero-3-phosphocholine].

In studying acetylation of 1-alkyl-sn-glycero-3-phosphocholine (lyso PAF) with acetic anhydride, a key step of the platelet activating factor (PAF) synthesis, we have found that in the presence of triethylamine or 4-dimethylaminopyridine some 1-alkyl-3-acetyl-sn-glycero-2-phosphocholine as an admixture to PAF formed, whereas the acid catalysed reaction resulted in isomerically pure PAF. The mechanism of the reaction leading to the PAF structural isomer is discussed.

Acetylation↗
PubMed1993

[Study of the interaction of alpha-tocopherol with phospholipids, fatty acids, and their oxygenated derivatives by (31)P-NMR spectroscopy].

Interaction of alpha-tocopherol with phospholipids, oleic, ricinoleic acids and linoleic acid hydroperoxides was investigated by means of 31P NMR spectroscopy on a model artificial membranes containing egg phosphatidylcholine and lysophosphatidylcholine. alpha-Tocopherol was shown to support the bilayer organization of lysophospholipids, whereas its introduction into the lecithin-water system stimulated the hexagonal phase formation. Free fatty acids exhibited a synergism to alpha-tocopherol, the effect of the hexagonal phase formation being at most increased by oxygenated acids--ricinoleic acid and linoleic acid hydroperoxides. In accordance with the experimental data, a conclusion about modifying and structuring action of alpha-tocopherol was made. Origin of the alpha-tocopherol's modulating effect on the membrane structure and a possible role of hexagonal phase forming upon its action in the course of peroxidation of lipids was discussed.

Fatty Acids↗
PubMed1985

The in vivo formation of nonbilayer lipid phase in E. coli membranes during the development of Ca2-dependent competence.

31P-NMR studies on E. coli cells reveal the in vivo formation of nonbilayer lipid structures, presumably of H11 phase, during Ca2-dependent competence induction. The data suggest the involvement of these structures in the exogenous DNA transfer into the cells during genetic transformation and transfection. The suggestion is supported by in vitro experiments in which the liposomes composed of different phospholipid species bind 14C-DNA in DNase and wash resistant form in conditions promoting the hexagonal phase formation.

Calcium↗
PubMed1984

[Synthesis and use of thiophosphatidylcholine in 31P-NMR study of membranes].

Thiophosphatidylcholines, i. e. phosphatidylcholine analogues in which one of phosphate oxygens is replaced by a sulfur atom, have been synthesized. The properties of aqueous dispersions of thiophosphatidylcholine and its equimolar mixture with diphosphatidylglycerol (cardiolipin) have been studied by 31P NMR. The 31P resonance of thiophospholipids dissolved in deuterochloroform was found to be shifted 19 ppm downfield from the signals of natural phospholipids. This feature allowed a complete separation of signals of thiophospholipids and natural phospholipids in the 31P NMR spectra of model membranes by using "DANTE" pulse sequence. The possibility of employing thiophospholipids in 31P NMR studies of lipid polymorphism in model membranes was demonstrated.

Chemical Phenomena↗
PubMedDate not supplied

[Immunomodulating properties of phospholipids].

Immunomodulating properties of glycerophospholipids were studied. Both phosphatidyl ethanolamines and phosphatidyl cholines exhibited similar immunostimulating effects.

5'-Nucleotidase↗