[Solid-phase enzymatic reactions. V. Comparison of catalytic properties of subtilisin and alpha-chymotrypsin in the absence of a solvent]. / Tverdofaznye fermentativnye reaktsii. V. Sravnenie kataliticheskikh svoistv subtilizina i alpha-khimotripsina v otsutstvie rastvoritelia.

Subtilisin Carlsberg (E.C. 3.4.21.14) catalyzes the hydrolysis of N-succinyl-L-phenylalanine p-nitroanilide in solid-state solvent-free hydrated protein-substrate mixtures. This process needs a certain critical degree of hydration of the protein molecule which is attained at the relative water vapour pressure (p/ps) above 0.49. The identical hydration dependency was found for the solid-state inactivation of subtilisin by phenylmethylsulphonylfluoride. Despite the fact that subtilisin and alpha-chymotrypsin belong to two different families of serine proteinases, the characteristics of their solid-state catalytic reactions are almost identical.

[The "protein-machine" concept and its consequences]. / Kontseptsiia "belok-mashina" i ee sledstviia.

Analysis is presented of the concept "protein-machine" and implying consequences, both of theoretical and experimental character. The approach "protein-machine" is compared with other approaches--"coherent excitation", "molecular dynamics" and "limited diffusion". In terms of the approach "protein-machine" valuable information inserted in the biological macromolecule and determining its functions is taken into account. It reflects the biological specificity and at the same time removes mystic shadow from this concept.

[Study of the structure of immunoglobins by small-angle x-ray diffraction. I. The structure of IgMCep in solution]. / Issledovanie stroeniia immunoglobulinov metodom rentgenovskogo malouglovogo rasseianiia. I. Struktura immunoglobulina MCep v rastvore.

The data of small-angle X-ray scattering from monoclonal immunoglobulin MCep (IgM) enabled the shape and geometrical parameters of the molecule in solution at 23 degrees C to be established. The molecule is a flat, strongly anisometric particle with radius of gyration 115 A, volume 1,8 X 10(6) A3, maximum size 380 A, thickness 35-40 A. The most probable molecular model in the approximation of homogeneous electron density in the molecule was suggested, its geometry fitting the experimental parameters. The five IgM subunits are located in the equatorial plane, low-electronic-density regions are located in the centre and at the periphery of the macromolecule. In addition, the absence of fixed angle values between Fab-regions in each subunit is indicative of rather high structural mobility at the periphery of the IgM molecule.

[Protonation of acridine in a hydrated protein matrix]. / O protonirovanii akridina v matritse gidratirovannogo belka.

Fluorescence of polycrystaline acridine in the matrix of solid alpha-chymotrypsin was studied at different humidities of the atmosphere. The fluorescence was not changed when the mixture was extensively dried. At intermediate and high humidities two consecutive processes proceed: 1) the solid-state dissolution of acridine crystals in the protein matrix and 2) the capture of protons by dispersed acridine molecules due to the proton transport through H-bound chains of water molecules from the protein proton-donor groups.

[Electromechanical model of an enzyme-substrate kompleksa]. / Elektromekhanicheskaia model' ferment-substratnogo kompleksa.

An electro-mechanical model is suggested for studying the hydrolytic reaction catalyzed by an enzyme having a domain structure. The fixation of the necessary set of reagents configurations by the enzyme molecule allows the reaction rate acceleration. The model suggests specificity of the enzyme action. The model makes more clear the phenomenon of complementarity between the unchanging part of the substrate molecule and the active site of the enzyme which require not only the spatial fit but also the agreement of some physical properties, such as atom and group partial charges. The model is selfconsistent, i. e. it is not contrary to the existing data on the structural and functional properties of enzyme proteins having the domain structure.

[Hydration of a preparation of total yeast tRNA]. / Issledovanie gidratsii preparata summarnoi drozhzhevoi tRNK.

The interaction of water molecules from the vapour phase with the total backer's yeast tRNA preparation was studied by the dynamic aquametric method. The primary hydration sites for processes of sorption and desorption of water molecules was evaluated by means of multilayer adsorption BET-equation. It was shown that the primary hydration sites are the oxygen atoms in the ribose-phosphate backbone of the tRNA molecule. The structure of surfaces of globular proteins and tRNA molecules were compared from the point of view of their ability to interact with water molecules. The higher degree of maximal hydration (under saturated water vapour or in aqueous solution) was considered as a result of regular arrangement of the most part of tRNA primary hydration sites.

[Effect of temperature on chymotrypsinogen A hydration in a dynamic system]. / Vliianie temperatury na gidratsiiu khimotripsinogena A v dinamicheskom rezhime.

The temperature dependence of chymotrypsinogen A was studied by a dynamic method. A gradual exclusion of low adsorbing centers out of the whole number of hydratation centers was observed during the raise of temperature. Differential isosteric heats of hydration were measured at different degrees of hydration. It was shown that at low hydration the heat absorption is connected with the conformational change of the protein molecule.

[Solid-state enzymatic reactions. II. Chymotrypsin hydrolysis of N-succinyl-L-phenylalanine n-nitroanilide]. / Izuchenie tverdofazykh fermentativnykh reaktsii. II. Khimotripsinovyi gidroliz n-nitroanilida N-suktsinil-L-fenilalanina.

There was studied the solid-state enzyme reaction of specific substrate N-succinyl-L-phenylalanine-p-nitroanilide hydrolysis in contact with alpha-chymotrypsin (Cht). It is shown that product yield is dependent on hydration of the protein. The product is formed only when the relative pressure of water vapours (p/ps) was higher than certain magnitude (p/ps) crit; which depends on the amount of the salt in the sample: the higher the salt concentration the lesser the (p/ps) crit value. It is suggested that the counter-ions may interact with some of primary hydration sites of the Cht molecule. Because of that for the formation of the active Cht conformation is enough to bind lesser number of water molecules than in salt-free samples. But in the presence of salt excess in Cht sample it is necessary to bind of the protein surface at least yields to 80 mol H2O/mol Cht.

[The actions of low-molecular fragments of substrate and their analogs on the activity of isoenzymes of phospholipase C from Clostridium perfringens]. / Deistvie nizkomolekuliarnykh fragmentov substrata i ikh analogov na aktivnost' izofermentov fosfolipazy s Clostridium perfringens tipa a.

The interaction of the lecithin molecule fragments and their analogues with phospholipase C Cl. perfringens was studied by gel-diffusion in agarose-lecithin gels. It was found intense inhibition of phospholipase C activity in the presence of cathionic compounds; this phenomenon shows the existence of anionic centre in the active site of enzyme. The esteric centre is probably hydrophobic nature and is not capable to bind the negatively charged groups. However, phosphoserine, phosphothreonine, gamma-aminobutyric, aspartic and glutamic acids can interact with an additional cathionic centre, whose location in phospholipase C differs from that in pancreatic phospholipase A2.

[Isotherms of globular protein hydration under dynamic conditions]. / Izotermy gidratsii globuliarnykh belkov v dinamicheskom rezhime

The hydration isotherms of alpha-chymotrypsin, lysozyme, pork insulin, pork pepsin and serum albumin were obtained by means of dynamic method. The values of BET-monolayers for processes of water sorption leads to (h) and desorption comes from (h) do not depend on the static or dynamic way of achieving of hydration equilibrium in spite of difference in the shape of isotherms. The values of comes from h for proteins with known tertiary structure (alpha-chymotrypsin, lysozyme and insulin) coinside with the number of exposed polar amino acid side chains. The lowering of leads to h values in comparison with comes from h is correlated with inability of omega-amido groups of Asn and Gln residues and of ion pair-forming residues to take part in the formation of sorptive BET-monolayer. These rules for the interpretation of hydration isotherms were used to evaluate the numbers of exposed and buried polar side chains in proteins with unknown tertiary structure--pepsin and serum albumin.

[Anionic center of porcine pancreatic phospholipase A2]. / Anionnyi tsentr pankreaticheskoi fosfolipazy A2 svin'i

The interaction between porcine pancreatic phospholipase A2 and low-molecular fragments of its substrate -- lecithine was studied using gel-diffusion of the enzyme in lecithin-agarose plates. When the inhibitor was added, a decrease in the magnitude of cleared areas (l/l0) around the depots filled with enzyme solution was observed. A marked decrease in l/l0 in the presence of alpha- and beta-glycerophosphates supported the statement that the cathionic center is a part of the enzyme active site SII. The potent inhibition of phospholipase activity in the presence of phosphocholine, choline, acetylcholine, thiocholine and acylthiocholines suggests the existence of an anionic center SIII in the active site. This suggestion is supported by intensive inhibition of phospholipase activity by certain, aliphatic amines. It was shown that the center is spaced in the direction of the cathionic center. SII. The main contribution to the binding of the cathionic lecithin part ("head") with the anionic center SIII is probably provided by the ion-ionic interactions.