[Interaction of a spin-labeled analog of ATP with myosin]. / Vzaimodeistvie spin-mechenogo analoga ATF s miozinom.

By means of spin labeled analogs of ATP we have shown that conformational changes in myosin molecule induced by variation of temperature take place in the region of the active centre. In case of Mg-ATP and unmodified myosin conformation of the active centre changes monotonously with the change in temperature but after the modification of S1 thiol groups by N-ethylmaleimide on the temperature dependence curve of rotational mobility of the spin label a discontinuous is observed at 14-16 degrees C. It is also observed in case of K+-EDTA-ATP, or Ca2+-ATP and unmodified myosin. It is shown that the chemical analogs of Mg2+-paramagnetic ion Mn2+ are directly connected with the myosin active centre in the presence of ATP(ADP), i. e. a triple complex enzyme-bivalent cation-substrate is formed.

[Effect of lyophilization on the free-radical state of animal cells]. / O vliianii liofilizatsii na svobodnoradikal'nye sostoianiia kletok zhivotnykh

The process of lyophylisation carried out very carefully under strictly defined conditions does not in inself bring about the changes in the parameters of the ESR signal with g approximately equal to 2.00 observed in animal cells. The free radicals responsible for the ESR signal observed under usual experimental conditions, result from a contact of the lyophylised specimen with moisture at an optimum water content of about 10%.

[Spin label study of plasma lipoproteins]. / Issledovanie lipoproteidov plazmy metodom spinovykh metok.

Lipoprotein structure was studied by means of EPR-spectroscopy of spin probes--iminoxyl derivatives of stearic acid and of androstane--in blood plasma of 40-59 years old men. The mode of wrapping of external monolayer of lipoprotein particles, the type of their intermolecular interactions were similar to corresponding characteristics of bilayer in biological and model membranes. Correlation was observed between concentration of separate lipoproteins in blood plasma and the structural parameters of the probe distribution in hydrophobic and polar regions of the lipoprotein preparations. The phenomena observed might be related to capacity of the high density lipoproteins to accept cholesterol from cell membranes with transfer of cholesterol into liver tissue, where it is subsequently metabolized, as well as to the property of the very low density lipoproteins to transfer cholesterol into tissues, particularly, into vascular walls.

[Conformational changes in soluble mitochondrial ATPase by the spin probe method]. / Izuchenie konformatsionnykh izmenenii v rastovorimoi mitokhondrial'noi ATPaze metodom spinovykh metok.

Modification of soluble mitochondrial ATPase (factor F1) by spin-labelled iodoacetamide and spin-labelled methyleneketone does not cause and change in the catalytic properties of the enzyme. The temperature dependence of tau corr. of labels bound to factor F1 testifies to conformational changes in the enzyme at temperatures of 18--20 degrees C and 34--37 degrees C. At these temperature intervals, breaks are observed in the temperature dependence of the ATPase reaction rate in the Arrenius plot. The results obtained indicate that the thermally induced conformational changes in factor F1 affect large areas of the protein molecule. The interaction of factor F1 with the hydrophobic spin probes, namely fatty acid derivatives, was studied. It was shown that the interaction of foctor F1 with Mg2+, Mg-ATP, Mg-ADP and ADP, results in an increase in the ability of the enzyme to adsorb spin probes.

[Tiron as a spin-trap for superoxide radicals produced by the respiratory chain of submitochondrial particles]. / Tairon kak spinovaia lovushka dlia superoksidnykh radikalov, obrazuemykh dykhatel'noi tsep'iu sybmitokhondrial'nykh chastits.

Tiron can be used as a spin-trap for O2 radicals generated by the respiratory chain of submitochondrial particles (SMP). Using this sensitive method, it was shown that the O2 (radical) production by the succinate-oxidizing SMP can be reduced by antimycin or 4-nonyl-2-hydroxyquinoline-N-oxide, the effects of both antibiotics being abolished and prevented by cyanide. It is suggested tht the O2 radicals are produced due to autooxidation of ubisemiquinone which is formed as an intermediate upon one-electron oxidation of CoQH2 by cytochrome c1. The effects of antimycin, 2-nonyl-4-hydroxyquinoline-N-oxide and cyanide on the O2 (radical) generation correlate with the effects of these inhibitors on a steady-state concentration of ubisemiquinone predicted by the Mitchell's Q-cycle hypothesis.