The 2.03 signal as an indicator of dinitrosyl-iron complexes with thiol-containing ligands.

The parameters of EPR signal from dinitrosyl-iron complexes (DNIC) with bovine serum albumin (BSA), horse hemoglobin (Hb), and apometallothionein (apo-Mt) of horse kidney incorporating one (BSA, Hb) or two thiol-containing ligands (apo-Mt) were compared. The EPR signal from DNIC-BSA was characterized by the rhombic symmetry of g tensor at room temperature of signal recording (ambient temperature) or at 77K in the solution frozen in the presence of glycerol. In freezing of the solution in the absence of glycerin, under the exposure of DNIC-BSA to negatively charged sodium dodecyl sulfate (SDS) ions, or in the incorporation of DNIC-BSA into the reversed micelles formed by negatively charged ions of surfactant aerosol OT, the symmetry of the g tensor of DNIC-BSA EPR signal increased to axial. A similarly high symmetry of g tensor was observed for the DNIC-Hb EPR signal in the absence of any influence on this protein complex. The shape of EPR signals from these preparations recorded at 77K was identical to that of EPR signal from DNIC with cysteine in frozen solution. In this connection it was concluded that the EPR signal from this low-molecular DNIC with the (RS-)2Fe+(NO+)2 structure cannot be considered as a peculiar "fingerprint" of DNIC with the same structure in biosystems. In such systems the same signal can originate from protein DNIC incorporating only one thiol-containing ligand along with a nonthiol ligand. The EPR signal displayed by DNIC with apo-Mt with a high content of cysteine residues at room temperature of registration was identical to the EPR signal from frozen solution of DNIC with cysteine. This protein DNIC is apparently characterized by the same structure as DNIC with cysteine.

[The effect of reversed micelles of cetyltrimethylammonium bromide on equilibrium constants and kinetics of oxidation-reduction reactions with the participation of cytochrome c]. / Vliianie obrashchennykh mitsell bromistogo tsetiltrimetilammoniia na konstanty ravnovesiia i kinetiku okislitel'no-vosstanovitelnykh reaktsii s uchastiem tsitokhrom c.

To model the effect of membrane environment on the electron transfer reactions we studied the thermodynamics and kinetics of the reactions of cytochrome c and 2,6-dichlorophenolindophenol with ferri- and ferrocyanide in the reversed micelles cetyltrimethylammonium bromide in chloroform/octan mixture. Incorporation of the protein in micelles leads to increasing the equilibrium constant (K1) up to 300 times. This effect is mainly due to a decrease in the ferrocytochrome c oxidation rate constant in the reaction with ferricyanide. Micellar solubilization of the dye also leads to a marked increase in the equilibrium constant K2. The estimations of the values K1 and K2 in water-alcohol mixtures and in aqueous micellar solutions of surfactant together with kinetical and spectral data show that the increase of K1 and K2 in reversed micelles is caused generally by redox potential changes of low-molecular reagents. The latter change their environment after adsorption on the micellar surface.

[A study of the effect of solvent composition and viscosity on the molecular dynamics of human serum albumin using Rayleigh scattering of Mössbauer radiation]. / Izuchenie vliianiia sostava i viazkosti rastvoritelia na molekuliarnuiu dinamiku syvorotochnogo al'bumina cheloveka metodom releevskogo rasseianiia messbauérovskogo izlucheniia.

By means of RSMR changes of human serum albumen intramolecular mobility by addition of 1.5% and 7.5% of glutar dialdehyde (GD) in concentrated protein solution, heat denaturation of a protein or substitution of water by water-glycerol solvent with amount of water to glycerol: 1 to 2 were studied. It is shown that the elastic fraction for HSA is changed much less addition of GD or by heat denaturation than by substitution of water solution by water-glycerol. It seems that the observed strong influence of glycerol on intramolecular mobility of HSA is connected mostly with effective dehydration of protein (by substitution of the part of a water solvent by glycerol) and with a small volume decrease of protein (due to preference hydration effect) rather than with the increase of the solvent viscosity.

[Comparative study of the kinetics of the reduction of cytochrome c and the nitroxide radical in reversed aerosol OT micelles in octane]. / Sravnitel'noe issledovanie kinetiki vosstanovleniia tsitokhroma c i iminoksil'nogo radikala v obrashchennykh metsellakh aérozolia OT v oktane.

The comparison of the reduction kinetics of cytochrome c and nitroxide radical by ascorbate in reversed micelles of aerosol OT in octane was studied. The plot of the dependence of the reduction rate constant on the micelle hydratation is bell-shaped in the case of protein but shows the plateau form for the radical. The reaction rates decreases at high micelle concentrations. The equations have been drawn that connect the experimental rate constants with intramicellar biomolecular rate constant (km) for reagents unsolved in organic phase. In the case of strong hydratated micelles km for the radical reduction is practically equal to the rate constant in aqueous solution. For cytochrome c the ratio of these constants is less than 0.22, that may be explained by protein conformational changes detected by optical methods. For small micelle hydratation the dependence of the cytochrome reduction rate on ascorbate concentration is characterized by plateau. Under these conditions the limited stage of reaction is apparently the transition of the protein to the active conformation.

[Effect of adsorption on the structure and properties of hemoglobin]. / Vliianie adsorbtsii na strukturu i svoistva gemoglobina.

Adsorption spectra of Hb+ and HbO2 adsorbed on silica and monolayers cholesterol supported on silica have been studied. It is shown that immobilization leads to new states of proteins, their properties depending on the nature of support and conditions of adsorption. Adsorption of haemoglobin leads to its inactivation. The rate of inactivation decreases with an increase of surface concentration of haemoglobin and with simultaneous adsorption of inert proteins.

[Conformation of cytochrome c, adsorbed on different substrates]. / Izuchenie konformatsii tsitokhroma c, adsorbirovannogo na razlichnykh nositeliakh.

Visible spectra of cytochrome c adsorbed on solid supports and on the same supports covered with monolayers of lecithin and cholesterol were studied. It was shown that absorption spectra of high spin cytochrome c and pK of transition from low to high spin form depend on the nature of adsorbent surface.

[Spectral characteristics of immobilized peroxidase]. / Issledovanie spektral'nykh kharakteristik immobilizovannoi peroksidazy.

Visible spectra of peroxidase adsorbed on insoluble supports were studied. It has been shown that immobilization leads to essential conformational changes of the enzyme which affect its bond with imidasol.