Bile Acids as Inducers of Protonophore and Ionophore Permeability of Biological and Artificial Membranes.

It is now generally accepted that the role of bile acids in the organism is not limited to their participation in the process of food digestion. Indeed, bile acids are signaling molecules and being amphiphilic compounds, are also capable of modifying the properties of cell membranes and their organelles. This review is devoted to the analysis of data on the interaction of bile acids with biological and artificial membranes, in particular, their protonophore and ionophore effects. The effects of bile acids were analyzed depending on their physicochemical properties: namely the structure of their molecules, indicators of the hydrophobic-hydrophilic balance, and the critical micelle concentration. Particular attention is paid to the interaction of bile acids with the powerhouse of cells, the mitochondria. It is of note that bile acids, in addition to their protonophore and ionophore actions, can also induce Ca2+-dependent nonspecific permeability of the inner mitochondrial membrane. We consider the unique action of ursodeoxycholic acid as an inducer of potassium conductivity of the inner mitochondrial membrane. We also discuss a possible relationship between this K+ ionophore action of ursodeoxycholic acid and its therapeutic effects.

The effect of mild heat stress of different frequencies on the adaptability of Drosophila melanogaster females.

In natural populations, insects regularly face an adverse impact of different natures: harsh weather swings, lack of food resources, the insecticidal treatment. We studied the effect of repeated episodes of mild heat stress of different frequencies on stress resistance of Drosophila melanogaster females. We found out that the mild heat stress (38°Ð¡, 1 hr) repeated daily within 2 weeks resulted in (a) an increased activity of the dopamine (DA) metabolism enzymes, DA-dependent arylalkylamine N-acetyltransferase and alkaline phosphatase, which suggested a decrease in DA level, and (b) an increased survival rate under acute heat stress (38°Ð¡, 4 hr). The same mild heat stress repeated weekly had no effect on these parameters.

Temperature sensitive supramolecular self assembly of per-6-PEO-ß-cyclodextrin and α,ω-di-(adamantylethyl)poly(N-isopropylacrylamide) in water.

The host/guest interactions in water of a star polymer consisting of a ß-cyclodextrin (ß-CD) core bearing six poly(ethylene oxide) arms linked to the C6 positions of ß-CD (ß-CD-PEO7, Mn 5000 g mol(-1)) and α,ω-di-(adamantylethyl)poly(N-isopropylacrylamide) (Ad-PNIPAM-12K, Mn 12,000 g mol(-1)) were studied by 1D and 2D (1)H and (13)C NMR spectroscopy, isothermal calorimetry (ITC), and light scattering (LS). In cold water (T < 26 °C) supramolecular "dumbbell" assemblies, consisting of PNIPAM chains with ß-CD/Ad inclusion complexes at each end, formed viaß-CD-insertion of the terminal Ads through the ß-CD secondary face. Light scattering, microcalorimetry (DSC), and DOSY NMR studies indicated that mixed aqueous solutions of ß-CD-PEO7 and Ad-PNIPAM-12K undergo a reversible heat-induced phase transition at ∼32 °C, accompanied by a release of a fraction of the Ad-bound ß-CD-PEO7 into bulk solution and the formation of aggregated Ad-PNIPAM-12K stabilized by a ß-CD-PEO7 shell.