[Modeling of damage to cell membranes during photodynamic therapy: photosensitization of planar lipid bilayers by hematoporphyrin dimethyl ether]. / Modelirovanie povrezhdeniia kletochnykh membran pri fotodinamicheskoi terapii: fotosensibilizatsiia ploskogo lipidnogo bisloia dimetilovym efirom gematoporfirina.

The variations of electrical conductance of planar bilayer lipid membranes (BLM) sensitized by hematoporphyrin dimethyl ether under visible light illumination were studied. The conductance of BLM does not change for some period after switching on the light, then an increase in the conductance starts and the membrane breaks. This "induction" time does not depend on addition of azide or ferricyanide to the solution, on addition of BHT to the lipid and on substitution of air for argon in the cell. The induction time for any new BLM, formed in the same cell immediately after the previous membrane was broken, is shorter. The variation of BLM boundary potentials during induction time was not observed. The results obtained suggest that the photodamage of BLM sensitized by HPD leads to accumulation of uncharged reaction products and oxygen does not take part in this process.

[Electrostatic method of determination of phospholipase A activity]. / Elektrostaticheskii metod opredeleniia aktivnosti fosfolipazy A.

An electrostatic assay of phospholipase A activity has been developed. This assay is based on the monitoring of changes in the boundary potential of the planar lipid bilayer. The initial rate of the potential changes induced by phospholipase hydrolysis is proportional to the enzyme activity. The sensitivity of the method is up to 0.0002 Units/ml; the effect of impurities is ignorable. The method allows the use of natural phospholipase substrates and is rapid, i.e., the phospholipase activity assay takes approximately 5 minutes.