[Interconnection of physico-chemical characteristics of organic solvents and their denaturing ability in relation to proteins]. / Vzaimosviaz' fiziko-khimicheskikh kharakteristik organicheskikh rastvoritelei s ikh denaturiruiushchei sposobnost'iu po otnosheniiu k belkam.

Reversible denaturation of several proteins (alpha-chymotrypsin, trypsin, laccase, chymotrypsinogen, cytochrome c and myoglobin) by a broad series of organic solvents of different nature was studied. The regularities of this process were analyzed, employing both experimental and literary data based on the results of kinetic and spectroscopic measurements. In all the systems under study denaturation proceeded in a threshold manner, i. e., an abrupt change in the catalytic and/or spectroscopic properties of the dissolved proteins was observed after a certain threshold concentration of the organic solvent had been reached. To account for the observed features of the denaturation process, a thermodynamic model of reversible protein denaturation by organic solvents was proposed. This model is based on the widely accepted viewpoint that the undisturbed water shell around the protein globule is necessary for maintaining the dissolved protein in the native state. Quantitative analysis of the model led to an equation establishing a relationship between the threshold concentration of an organic solvent and its physico-chemical characteristics, such as hydrophobicity, solvating ability and molecular geometry. This equation fits well in the experimental data for all the proteins tested. Based on the above thermodynamic model of protein denaturation, a novel quantitative parameter characterizing the denaturing strength of organic solvents (termed as the denaturation capacity or DC) was proposed. Different organic solvents arranged according to their DC values form the DC scale of organic solvents which permits to predict theoretically the threshold concentration of any organic solvent for a given protein.(ABSTRACT TRUNCATED AT 250 WORDS)

[Conformation and reduction-oxidation properties of cytochrome c incorporated into reversed micelles of a surfactant in an organic solvent]. / Konformatsiia i okislitel'no-vosstanovitel'nye svoistva tsitokhroma c, vkliuchennogo v obrashchennye mitselly poverkhnostno-aktivnogo veshchestva v organicheskom rastvoritele.

Changes observed in CD- and absorption spectra of cytochrome c solubilized in reversed micelles AOT showed significant structural transformations of protein in the region of the active centre and particularly revealed a replacement of the sixth ligand of heme iron. These changes also affected the redox properties of cytochrome c.

[Enzymes incorporated into reversed micelles of surfactants in organic solvents. Study of the protein-aerosol OT-H2O-octane system by sedimentation analysis]. / Fermenty, vkliuchennye v obrashchennye mitselly poverkhnostno-aktivnykh veshchestv v organicheskikh rastvoriteliakh. Issledovanie sistemy belok--aérozol' OT--H2O--oktan metodem sedimentatsionnogo analiza.

Using ultracentrifugation, the systems of reversed micelles of aerosol OT in octane containing solubilized protein (alpha-chymotrypsin, lysozyme, trypsin, egg albumin, alcohol dehydrogenase from horse liver and gamma-globulin) were studied. The changes in the sedimentation coefficients of reversed micelles during incorporation of the protein are correlated (within a wide range of experimental conditions, e. g. degree of surfactant hydration or protein concentration) exclusively with the molecular weight of the solubilized protein. The simplest solubilization model, according to which the protein molecule is incorporated into the inner cavity of the reversed micelle at the stoichiometric ratio of 1 : 1, which does not affect the external sizes of the reversed micelle, has been proposed. Using alpha-chymotrypsin as an example, the conditions, under which the sedimentation properties of the systems deviate from this model, have been found. These deviations occurred at sufficiently low degrees of the surfactant hydration, when the inner cavity of the reversed micelle is smaller than the effective size of the solubilized protein molecule. In the latter case the protein forms a new micelle of necessary (i. e. larger) size. Since the hydrated micelle can be regarded as an elementary (30-100 A) fragment of biomembranes, the results obtained should be taken into consideration when analyzing the structural organization and functioning of the latter.