The immobilization of the enzymeE. coli L-asparaginase on polysaccharides. III. Covalent binding with 3-bromo-2-hydroxypropyldextran

The synthesis of immobilized L-asparaginase on 3-bromo-2-hydroxypropyldextran has been effected. Some physicochemical properties of the preparations obtained have been studied. A stabilizing effect of the modification on the heat stability of the L-asparaginase has been detected. The influence of the bound polymer on the antigenic properties of the enzyme have been established.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 224–228, March–April, 1981.     

Immobilization of the enzyme L-asparaginase fromE. coli on polysaccharides. II. Covalent binding with soluble CM-cellulose

The covalent binding of L-asparaginase to soluble CM-cellulose has been carried out by the azide method, and some physicochemical properties of the preparation obtained have been studied. It has been established that the modified L-asparaginase possesses a higher heat stability than the native enzyme and also a greater resistance to proteolytic enzymes.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 383–388, May–June, 1979.     

Immobilization of the enzyme L-asparaginase fromE. coli on polysaccharides IV. Covalent binding with dialdehyde-dextran

The synthesis has been effected of immobilizedE. coli L-asparaginase on medical dextran — poliglyukin. The influence of the bound polymer on some physicochemical properties of the final products have been studied. An increased resistance to heat and stability on storage of the immobilized forms of L-asparagine in comparison with a native enzyme has been found. It has been shown that the polymer modification of L-asparaginase leads to a decrease in the antigenic affinity of the immobilized enzyme as compared with the native enzyme.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. All-Union Scientific-Research Technological Institute of Antibiotics and Enzymes for Medical Purposes, Leningrad. A. Kirkhenshtein Institute of Microbiology, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 766–771, November–December, 1986.     

Immobilization of the enzymeL-asparaginase fromE. coli on polysaccharides. VI. Preparation and properties of polymeric derivatives based on dextran carbonates

Methods have been developed for obtaining soluble and insoluble dextran carbonates. The addition of the latter to E. coli L-asparaginase has given water-soluble, gel-like, and insoluble forms of the immobilized enzyme. The influence of the bound polymer on some physicochemical properties of L-asparaginase has been determined. The antileukemic action of soluble dextran derivatives of L-asparaginase has shown that their efficiency is greater than that of the native enzyme.A. Kirkhenshtein Institute of Microbiology, Latvian Academy of Sciences, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 432–436, May–June, 1993.     

L-asparaginase bound in a polyacrylamide gel

Summary The enzyme L-asparaginase fromE. coli has been included in polyacrylamide gel, and some of its properties have been investigated: stability, pH dependence, heat stability, K_m. It has been shown that the enzymegel obtained has a better stability then the native enzyme.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 382–384, May–June, 1976.     

Chemical modification of the tryptophan residues of the L-asparaginase of E. coli with N-bromosuccinimide

Summary The role of the tryptophan residues in the L-asparaginase molecule has been studied by the method of chemical modification with N-bromosuccinimide, and it has been established that in an acid medium this reagent modifies all four tryptophan residues present in the molecule, completely suppressing the activity of the enzyme.The substrate — L-asparagine — and a competing inhibitor — S-benzyl-N-benzyloxycarbonyl-L-cysteine — protect the L-asparaginase from the action of N-bromosuccinimide, which shows the role of the tryptophan in the catalytic center of the L-asparaginase.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 228–231, March–April, 1975.     

Immobilization of the enzyme L-asparaginase of E. coli on polysaccharides. V. Preparation and properties of polymeric conjugates based on water-soluble CM-cellulose differing by the quantitative amounts of polymer

A precedure has been developed for the chemical binding of L-asparaginase to soluble CM-cellulose which permits final immobilization products with different degrees of modification to be obtained. Some physicochemical and immunological properties of the samples obtained have been studied.A. Kirkhenshtein Institute of Microbiology, Latvian SSR Academy of Sciences, Riga. All-Union Scientific-Research Technological Institute of Antibiotics and Enzymes for Medical Synthesis, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 581–587, July–August, 1987.     

Immobilization of the enzyme E. coli L-asparaginase on a water-soluble copolymer of vinylpyrrolidone and acrolein

A method for immobilizingE. coli L-asparaginase on a copolymer of vinylpyrrolidone and acrolein has been developed and optimized. The influence on the nature of the modification of the number of acrolein residues in the copolymer has been established. The enzymatic and some physicochemical properties of the immobilized forms of the enzyme obtained have been studied.A. Kirkhenshtein Institute of Microbiology, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 562–565, July–August, 1988.     

Immobilization of the enzyme L-asparaginase fromE. coli on polysaccharides IV. Covalent binding with dialdehyde-dextran

The synthesis has been effected of immobilizedE. coli L-asparaginase on medical dextran — poliglyukin. The influence of the bound polymer on some physicochemical properties of the final products have been studied. An increased resistance to heat and stability on storage of the immobilized forms of L-asparagine in comparison with a native enzyme has been found. It has been shown that the polymer modification of L-asparaginase leads to a decrease in the antigenic affinity of the immobilized enzyme as compared with the native enzyme.     

Immobilization of the enzymeL-asparaginase fromE. coli on polysaccharides. VI. Preparation and properties of polymeric derivatives based on dextran carbonates

Methods have been developed for obtaining soluble and insoluble dextran carbonates. The addition of the latter to E. coli L-asparaginase has given water-soluble, gel-like, and insoluble forms of the immobilized enzyme. The influence of the bound polymer on some physicochemical properties of L-asparaginase has been determined. The antileukemic action of soluble dextran derivatives of L-asparaginase has shown that their efficiency is greater than that of the native enzyme. A. Kirkhenshtein Institute of Microbiology, Latvian Academy of Sciences, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 432–436, May–June, 1993.     

Reductive alkylation ofE. coli L-asparaginase

Alkylasparaginases have been obtained with the far-reaching modification of 1–10 lysine residues per subunit of the enzyme. It has been established that alkylation does not affect the stability of the enzyme, and the change in the pH optimum of the catalytic action is due to the chemical nature of the alkyl substituent.Institute of Organic Synthesis, Academy of Sciences of the Latvian SSR, Riga. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 232–235, March–April, 1980.     

Synthetic analogs of Peganum alkaloids VI. Photochemical oxidation of 2,3-polymethylene-quinazoline derivatives

The rates of the photochemical oxidation of quinazoline alkaloids — deoxypeganine, peganine, pentamethylenequinazoline, and peganol — to the corresponding oxo derivatives have been studied. It has been shown by HPLC that the oxidation of deoxypeganine proceeds through a stage of the formation of a carbinolamine (peganol); in the case of its hydrochloride, the reaction takes place by the same scheme but four times more slowly. Tetra- and pentamethylenequinazolines have been synthesized and information on their melting points in the literature has been corrected. In the series trimethylenequinazoline-pentamethyl-enequinazoline-tetramethylenequinazoline the stability falls from left to right.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 528–532, July–August, 1991.     

Experimental and calculated complex formation curves for mixed, dynamic and semi-dynamic, metal–ligand systems.: A differential pulse polarographic study of Cu–sarcosine–OH and Cd–MIDA–OH systems at a fixed ligand to metal ratio and varied pH

The Cu–sarcosine–OH and Cd–MIDA–OH systems have been studied by differential pulse polarography (DPP) at a fixed total ligand to total metal concentration ratio and varied pH at 298 K and μ=0.5 mol dm⁻³ in the background of NaNO₃. Both the metal–ligand systems show initially dynamic (labile), followed by semi-dynamic behaviour on the DPP time scale. It has been shown that the experimental and calculated DPP complex formation curves used previously only for labile metal–ligand systems can be employed for the modelling of all species formed in a solution and optimisation of their stability constants. The stability constants of ML and ML₂ complexes as log β were estimated for Cu^II and Cd^II as 7.75±0.02, 14.49±0.01 and 6.67 ±0.02, 12.00±0.02, respectively (all known hydroxide species of copper and cadmium, including polynuclear species, were incorporated into the metal–ligand–OH systems). The formation of the complex CuL₂(OH) is suggested also and its stability constant as log β has been estimated to be 16.2±0.2. Results reported here seem to be reasonable when compared with the literature data reported at 298 K and different ionic strengths.     

Synthesis of new analogs of valinomycin and their properties. I

Conclusions 1. The synthesis of five valinomycin analogs differing by the configurations of the amino-acid and hydroxy-acid residues and also by the volumes of the radicals of the hydroxy-acid residues has been effected.2. The stability constants of the complexes of these analogs with potassium ions in ethanol solution have been determined.3. The antimicrobial activities of the compounds obtained have been studied and a correlation has been found between the degree of activity and stability of the complexes with K⁺.M. M. Shemyakin Institute of the Chemistry of Natural Compounds, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 233–240, March–April, 1974.     

Functional properties of “cotton protein.” II. Emulsifying properties of cotton protein isolates obtained by extraction with acid

It has been shown that a cotton seed protein isolate obtained by extraction with acid possesses a high emulsifying activity. The level of activity depends substantially on the pH of the medium and the method of precipitating the proteins. The stability of an emulsion obtained on the basis of the cottonseed isolated studied depends on its solubility.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 357–359, May–June, 1986.     

Rheological properties of interphase adsorption layers of gossypin at a liquid-liquid phase separation boundary. III. Influence of chemical modification

The rheological properties of interphase absorption layers of gossypin derivatives at liquid phase separation boundaries and the stability of benzene emulsions have been investigated. It has been shown that the acylation of gossypin with acetic and succinic anhydrides lowers the strength properties of the adsorption layers of protein, leading to a change in the stability of benzene emulsions stabilized by gossypin.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, FAX (3712) 89-14-75. M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 528–533, July–August, 1994.     

Ab initio and density functional theory based studies on collagen triplets

An understanding of the amino acid sequence dependent stability of polypeptides is of renowned interest to biophysicists and biochemists, in order to identify the nature of forces that stabilize the three-dimensional structure of proteins. In this study, the role of various collagen triplets influencing the stability of collagen has been addressed. It is found from this study that proline can stabilize the collagen triplet only when other residues are also in the polyproline II conformation. Solvation studies of various triplets indicate that the presence of polar residues increases the free energy of solvation. Especially the triplets containing arginine residues displays a higher solvation free energy. The chemical hardness of all the triplets in collagen-like conformation has been found to be higher than that in the extended conformation. Studies on Gly–X–Y, Gly–X–Hyp, and Gly–Pro–Y triplets confirm that there will be local variations in the stability of collagen along the entire sequence.     

Effective length of the alkyl chain and thermal behaviors of Langmuir–Blodgett films of octadecylammonium laurate, octadecylammonium octadecanoate and octadecylammonium tetracosanoate

Thermal behaviors of 11-layer Langmuir–Blodgett (LB) films of the double long-chain compounds of octadecylammonium laurate (ODALA), octadecylammonium octadecanoate (ODASA) and octadecylammonium tetracosanoate (ODATA) have been investigated by Fourier transform infrared spectroscopy. The temperature-dependent infrared spectra show that thermal stability of the three kinds of LB films depends upon the length of the hydrocarbon chain. The LB film of ODALA undergoes an order–disorder transition in the temperature range of 50–65 °C. In contrast, the ODATA LB film has the phase transition temperature range of 80–90 °C. Of particular interest is that both ODASA and ODATA LB films have nearly the same phase transition temperature range of 80–90 °C, indicating that the replacement between tetracosanoic acid and stearic acid has little effect on the thermal stability of the two compounds. The above observations suggest that the effective length of the alkyl chains, which is determined by the component with a shorter chain in the double long-chain compounds, has a dominant influence on the thermal stability. It is very likely that the whole chain of the shorter chain component such as octadecylamine in ODATA has contribution to the thermal stability while only the effective length of the longer alkyl chain component gives a significant effect.     

Stability of stationary catalysts in the hydrogenation of rapeseed oils

The stability of a nickel-copper-molybdenum-aluminum catalyst without additives and with the addition of promoting metals (chromium and titanium) in the hydrogenation of rapeseed oils has been investigated. It has been established that the addition of a promotor to the composition of a known catalyst raises the activity and improves the stability of the alloy. The possibility has been revealed of using catalysts that have been poisoned by sulfur compounds, after their regeneration.Al-Biruni Tashkent Polytechnic Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 600–604, September–October, 1990.     

The role of Hartree-Fock instability in calculations on electron transitions and polarizability for simple molecules

The stability problem is discussed for the Hartree-Fock solutions for simple molecules; the nonempirical GAUSSIAN-76 program has been supplemented with modules that enable one to monitor the course of the self-consistent calculation by means of stability matrices. The process is illustrated by a calculation on the nitrogen molecule.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 21, No. 1, pp. 94–97, January–February, 1985.