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The conjugate of the gossypol derivative megosin (1) with N-polyvinylpyrrolidone named rometin (2) was synthesized. The effects of 1 and 2 on the structure and permeability of human erythrocytes and rat liver mitochondria were compared. Compound 1 induced dose-dependent erythrocyte hemolysis and increased mitochondrial permeability, with concomitant changes in membrane structure as determined by ESR and fluorescence anisotropy methods. Immobilization of 1 on N-polyvinylpyrrolidone (compound 2) increased its water solubility and reduced the intensity of its effects on erythrocyte membrane integrity and mitochondrial permeability, which correlated with a decrease in the membranes structural changes induced by the compound. Although the same concentrations of free and N-polyvinylpyrrolidone bound 1 were used, far less (14)C-labeled 1 was incorporated into the membranes from complex than free 1. The increase in water solubility and the reduction of membrane-active properties of 1 after immobilization on N-polyvinylpyrrolidone could explain our previous observation of the decreased toxicity of 1.

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Circularly polarized chlorophyll luminescence (CPL) was recently shown to be an effective tool for the study of chiral macroaggregate formation of the light-harvesting chlorophyll a/b pigment–protein complexes (LHCIIs) in isolated chloroplasts. The CPL measuring system was modified to study green leaves. Spectral and intensity features of pea leaf CPL signals suggested that CPL indeed detected chiral macroaggregates. The signals were found to depend on the excitation vs emission optical alignment, as well as on the side (adaxial or abaxial) of the leaf. Illumination of attached leaves with either low intensity or strong photoinhibitory light did not affect the chiral macroaggregation status. In contrast, the induction of drought stress in detached leaves led to full disruption of the chiral macroaggregates. The disruption developed gradually during slow dehydration, whereas under fast, heat-stimulated dehydration it was manifested in cooperative diminution of both CPL and photochemical capacity. Simultaneous exposure of the leaves to photoinhibitory illumination and fast dehydration resulted in negative CPL signals. The results demonstrate the potency of CPL as a non-destructive tool for structural studies of LHCII in intact leaves under varying environmental conditions.

Abstract:In this paper, we present the results of a study on the membraneactive properties of gossypol, its derivatives and their polyvinylpyrrolidone complexes as assessed by differential scanning calorimetry and by the fluorescent probe method. The latter revealed the change in polarization of the incident radiation caused by the action of the polyphenol on the artificial membrane lipid matrix.