[Membranothropic properties of the urocanic acid].

The effects of urocanic acid (UA) on thermodynamic parameters of model dipalmitoylphosphatidylcholine (DPPC) lipid membrane have been studied by means of differential scanning calorimetry (DSC). The observed ordering effect of UA on the lipid bilayer is reflected in the increase in both the main phase transition temperature and cooperative unit size of the lipid membrane. Analysis of FTIR spectra suggests localization of UA molecules in the vicinity of the polar heads and carbonyl groups of DPPC due to electrostatic interactions and H-bonds. On the basis of experimental data obtained and geometry parameters of UA and DPPC molecules, some variants of the UA localization in DPPC bilayer were discussed.

[Univalent ions in phospholipid model membranes: thermodynamic and hydration aspects].

By means of differential scanning calorimetry, effects of systematic series of Group I and VII ions on the phase state of model multibilayer dimyristoylphosphatidylcholine (di(14:0)PC) membranes have been studied at a lipid/ion molar ratio of 3/1. The sign-changing correlations between the ionic radii of cations and temperature shifts of di(14:0)PC phase transition were obtained. For cosmotropic Li+ and Na+, the observed shifts were positive (LiCl: deltaT(m) = 0.6 degrees C; deltaT(p) = 1.9 degrees C), whereas chaotropic K+ and Rb+ presence resulted in negative shifts (RbCl: deltaT(m) = -0.3 degrees C; deltaT(p) = -2.5 degrees C). The anions (Cl-, Br-, I-) showed a similar effect increasing with the ions chaotropicity. An essentially weaker effect of Cs+ as compared to other alkali metal ions (CsCl: deltaT(m) approximately 0 degrees C; deltaT(p) = -0,1 degrees C) can be one of the reasons of its accumulation in living organisms. Generalization of all available data allowed us to specify some important factors of lipid-ion interactions that should be taken into account in further investigations in this field.

[Analysis of temperature and radiation-induced effects in model and natural biomembranes using UV-spectroscopy method]. / Issledovanie temperaturnykh i radiatsionno-indutsirovannykh éffektov v model'nykh i prirodnykh biomembranakh metodom uf-spektroskopii.

Effects of low-dose gamma-irradiation (up to 1 R) upon UV absorption spectra of water dispersions of egg yolk lecithin (1:1) and samples of rat liver homogenate were studied. Clearly detectable changes could be observed in the 200-220 nm range already under dose loads of several mGy. Radiation sensitivity was shown to be essentially temperature dependent, being the highest at physiological temperatures.

[Effect of radiation on the structure of model and natural biomembranes using differential scanning calorimetry]. / Issledovanie vliianiia radiatsii na strukturu model'nykh i prirodnykh biomembran metodom differentsial'noi skaniruiushchei kalorimetrii.

A novel method of DSC studies of biomembranes has been proposed, making it possible to investigate the influence of ionizing radiations upon the structure of water dispersions of phospholipids and phospholipid-based systems of natural origin, e.g., rat liver homogenates and erythrocyte ghosts. It is shown that in certain concentration range of the bonded water thermograms obtained are reproducible during heating and cooling cycles and can give information about phase state, supramolecular ordering and radiation sensitivity of the systems under consideration.