[Interaction of Bacillus intermedius 7P ribonuclease with ligand-free serum albumin]. / Vzaimodeistvie ribonukleazy Bacillus intermedius 7P s bezligandnym syvorotochnym al'buminom.

The efficiency of the binding of RNase 7P molecules to albumin on cocondensation with the aim of producing the prolonged action forms of the enzyme can be increased by using ligand-free human serum albumin (LFHSA). The CD method showed that LFHSA underwent changes of the cooperative character under the action of acid and urea. On potentiometric titration the number of titrated groups of LFHSA decreased with time. The GPC method demonstrated the RNase bound more efficiently to freshly dissolved LFHSA. In this case part of the enzymic activity was manifested only after proteolysis of the albumin carrier. Cocondensation with the aid of glutaraldehyde resulted in the formation of LFHSA-RNase conjugates composed of 1-2 moles of human serum albumin and 1-6 moles of RNase. More than 50% of transferase activity retained in the blood plasma for 2-3 days after intravenous injection of the conjugates with a molecular weight of 70-80 kD to rabbits.

[Enzymatic and conformational stability of polymeric complexes of alpha-amylase]. / Fermentativnaia i konformatsionnaia stabil'nost' polimernykh kompleksov alpha-amilazy.

The enzymatic and conformational stability of Bacillus subtilis alpha-amylase and its polymeric complexes in acid media and subsequent renaturation in weakly alkaline media were investigated. The following parameters of alpha-amylase secondary structure were determined from circular dichroism spectra: helical units -25%, beta-structures -9%; beta-turns -13%; disordered conformations -53%. After complexation with polymethacrylic acid (PMAA) the alpha-amylase secondary structure did not change, and the tertiary structure underwent only small local changes. Complexation of alpha-amylase with linear and cross-linked PMAA led to an increase in both enzymatic and conformational stabilities in acid media. Purification of alpha-amylase using a biosorbent resulted in higher acid resistance of the free enzyme and of that in the complex with PMAA. Moreover, the degree of reversibility of the acid inactivation also increased.

[Conformation properties and enzymatic activity of pancreatic ribonuclease in soluble complexes with sodium dextran sulfate]. / Konformatsionnye svoistva i fermentaltivnaia aktivnost' pankreaticheskoi ribonukleazy v rastvorimykh kompleksakh s natrievoi sol'iu dekstransul'fata.

Effect of complex formation with dextran sulfate (DS) (substitution degree 1.3, molecular mass 500 thousand) on RNAse enzymic activity. its spatial structure and conformation stability was studied. Hydrolytic activity of the enzyme in complex in inhibited already at small additions of DS, while the transferase one is changed only at a great excess of the polyelectrolyte. It has been shown by CD spectra that no notable conformation changes proceed in the enzyme during complex formation, although the enzyme turns destabilized to the denaturing effect of heat at the expense of strengthened interactions between DS and RNAse during its denaturation. Thus the inhibition of hydrolytic activity in the complex is primarily related to limitations for the formation of the enzyme-substrate complex on polyelectrolyte charged likely with the substrate, and not to the protein conformation changes.

[Effect of polymer modification of insulin on its enzymatic hydrolysis and conformation properties]. / Vliianie polimernoi modifikatsii insulina na ego fermentativnyi gidroliz i konformatsionnye svoistva.

AI, B29 insulin polymeric derivatives in which the polymeric chains (N-polyvinylimidazole, N-polyvinylpyrrolydone and polyacrylic acid) are bonded to the insulin molecule at one point were synthesized. The hydrolysis of the modified insulin by trypsin is dependent to a great extent on the chemical nature of the modifying polymer and is virtually independent of its molecular weight up to 20 kD. The effect of the modifying polymer manifests itself mainly in a change of the Michaelis constant. Investigation of the conformational properties of the insulin derivatives by the method of optical rotatory dispersion revealed that insulin modification by polymers caused a decrease of the amino acid content in the alpha-helical sequence from 41 to 33-30%. The chemical nature of the modifying polymer and its molecular weight have a profound effect on the conformational stability of the residual spatial structure of the modified insulin in alkaline media.

[Effect of the degree of modification of trypsin amino groups with polymers on the enzymatic and conformation properties of the protein]. / Izuchenie vliianiia stepeni modifikatsii aminogrupp tripsina polimerami na fermentativnye i konformatsionnye svoistva belka.

Trypsin was modified by introducing fragments containing an azo-bond into its molecule by the reaction of free amino groups of the enzyme with an azide of 2,2'-azobisisobutryic acid. Subsequently free-radical polymerization of N-vinyl pyrrolidone was carried out with the high molecular weight initiator obtained. The degree of modification of amino groups in trypsin was n = 6 divided by 12, which distinguishes this type of modification from that earlier proposed by the authors. In that case dichlorohydrate of dimethylimidate of 2,2'-azobisisobutyric acid was used for introducing azo-bonds into the molecule of the protein, n being equal to 2-3. It is shown that under the conditions of autolytic degradation both high molecular weight initiator based on trypsin and the trypsin-PVP (poly-N-vinyl pyrrolydone) covalent conjugates exhibit higher stability than initial trypsin. The method of circular dichroism was used for comparison of conformational properties of the modified trypsin forms. An increase of the rate of thermal inactivation was found to result from conformational changes occurring on modification of the enzyme.

[Synthesis and analysis of des-Met5-[D-Ala2]enkephalinamide analogs]. / Sintez i izuchenie analogov des-Met5-[D-Ala2]énkefalinamida.

The effects of N- and C-terminal oligoalanine insertions into des-Met5-[D-Ala2]enkephalin amide (I) on the biological activity and spatial structure were examined. The corresponding analogues were obtained by solid-phase synthesis using Sephadex LH-20 ac a polymeric support. Biological activity was assayed via changes in the pain threshold in the rat, body temperature, and also as affinity for opiate receptors. Active analogues were obtained upon modifying the carboxylic group in the tetrapeptide I with di- and tri-D-alanyls. The CD spectra of the C-derivatized analogyes were similar to those of the starting tetrapeptide I and [Met5]enkephalin, whereas the N-derivatized analogues showed essentially different CD spectra.

[The conformation properties and conformation stability of streptokinase and its polymer derivative]. / Izuchenie konformatsionnykh svoistv i konformatsionnoi stabil'nosti streptokinazy i ee polimernogo proizvodnogo.

The properties and conformational stability of the proteinaceous activator of fibrinolysis--native streptokinase--and its derivative obtained by modification with a linear hydrophilic copolymer based on N-vinylpyrrolidone, were studied by the circular dichroism method. It was shown that polymeric modification of streptokinase had no effect on the secondary structure, while the conformational stability of the modified protein to urea was higher than that of the native one. Studies on thermal stability of both native and modified forms of streptokinase showed that the inactivation rate was lower in the modified form as compared to the native one.

[Analysis of the secondary structure of urokinase by the circular dichroism method]. / Issledovanie vtorichnoi struktury urokinazy metodom krugovogo dikhroizma.

The secondary structure of urokinase with molecular weight 33 000 dalton was studied by the circular dichroism method. The secondary structure parameters were calculated based on the protein reference CD spectra resulted in the following secondary structure parameters: approximately 30% aminoacid residues constitute the alpha-helical regions, the same amount forms the beta-structure and an essential fractions contributes the beta-turns. Conformational stability of urokinase to alkaline pH (up to 11.6) and high temperature (up to 80 degrees) in 0.1 M phosphate buffer pH 6.6 was found.

[Synthesis of trypsin polymer derivatives with single-point binding of the polymer-modifier and protein]. / Sintez polimernykh proizvodnykh tripsina s odnotochechnym polimera-modifikatora s belkom.

In order to produce carbon-chain covalent "star-like" conjugates of trypsin, the latter was modified by attachment of fragments containing the reaction-capable azo-bond and then N-vinyl pyrrolidone was polymerized on the resultant high molecular weight initiator. The molecular weight and proteolytic activity of the compounds were determined, and their thermal stability and resistance to autolysis were investigated. It was shown that the trypsin modified by poly-N-vinyl pyrrolidone of different molecular weights acquired greater resistance to autolytic and thermal denaturation. The spectropolarimetric examination of the conformation properties of the modified trypsin forms at varying pH demonstrated that attachment of azo-bond containing fragments to the enzyme molecule destabilized its native structure in acidic pH areas while subsequent poly-N-vinyl pyrrolidone modification increased the area of pH-stability of the conjugate as compared to the native trypsin.

[Intramolecular modification of azisobutyrylinsulin and the use of the modified hormone for the synthesis of polymeric derivatives]. / Sintez vnutrimolekuliarno sshitogo azoizobutirilinsulina i poluchenie na ego osnove polimernykh proizvodnykh gormona.

An intramolecular modification of insulin at the alpha-amino group of glycine (A1) and the epsilon-amino group of lysine (B29) was carried out. The modification resulted in a slight alteration of the insulin secondary structure; the modified hormone possessed a biological activity which was practically identical to that of the natural hormone. Therefore the modified insulin can be used as a high molecular weight physiologically active radical inducer for the synthesis of (A1-B29) polyvinylimidazole derivatives. The molecular weight of the covalently linked polymer can be variable. It was shown that the increase in the amount of modifying polymer in the conjugate results in stabilization of the insulin secondary structure concomitant with a decrease of the biological activity and, moreover, of the immunoresponsiveness of the hormone.

[Study of the secondary structure of L-asparaginase over a broad range of pH values]. / Issledovanie vtorichnoi struktury L-asparaginazy v shirokom intervale znachenii pH.

Conformation of L-asparaginase from E. coli had been studied by spectropolarimetry methods (CD and ORD) in pH region from 2.5 to 12.5. Results were correlated with the change in enzyme activity. It was shown that the secondary structure of the enzyme degraded when pH was smaller than 5 and larger than 10. Degradation was accompanied by the dissociation of the agregative form on individual subunits. In pH region form 5 to 10 the secondary structure of L-asparaginase does not change. Secondary structure parameters of L-asparaginase calculated from the known aminoacid consequence by means of two independent theoretical methods are in satisfactory agreement with results of CD and ORD analysis spectra. It is proposed that there exists a hydrofobic slit into which the decapeptid containing serine from the L-asparaginase active site is plunged.

[Synthesis and properties of insulin modified on phenylalanine of chain B]. / Sintez i izuchenie insulina modifitsirovannogo po fenilalaninu tsepi B.

Lysyl and tetralysyl derivatives of insulin on phenylalanine of chain B were synthesized. The effects of modifications on the spatial structure and biological properties of the hormone were studied. It was found that an increase in the length of the modifier leads to a distortion of the hormone spatial structure resulting in a decrease of its biological activity.

[Effect of pH on the conformation properties and enzyme activity of alpha-amylase from Aspergillus terricola]. / Vliianie pN sredy na konformatsionnye svoistva i fermentativnuiu aktivnost' al'fa-amilazy iz Aspergillus terricola.

The effect of pH values on the conformation state of the protein globule and enzyme activity of alpha-amylase isolated from the culture liquid of the fungus Aspergillus terricola was studied. By the method of dispersion of optical rotation, it was demonstrated that together with the disordered structure the alpha-amylase macromolecule in its native form contained alpha-helix and beta-structures. With a pH change the enzyme macromolecule showed two conformational transformations: with a pH decrease from 4.0 to 2.0 alpha-helix uncoiled, and with a pH increase from 8.0 to 12.0 beta-form degraded. Hydrolytic activity of alpha-amylase was found to vary symbatically with the specific optic rotation in the above pH range.