Mass-spectrometric study of permethyl compounds of group IVB elements

Russian Chemical Bulletin -     

Highly selective mono-substitution in Pd-catalyzed cross-coupling reactions of 3,6-dichloropyridazine with organozinc compounds

Pd-catalyzed cross-coupling reactions of 3,6-dichloropyridazine (1) with benzyl, aryl, and alkyl organozinc compounds led to selective mono-substitution of one of the chlorine atoms. The subsequent cross-coupling of the resulting monochlorides with RZnCl afforded unsymmetrical 3,6-carbon-disubstituted pyridazines.     

Immobilization of carboxylic proteinases on amino-Silochrome

Summary Highly purified porcine pepsin and aspergillopepsin A immobilized on amino-Silochrome have been obtained. The enzymatic properties of these insoluble derivatives have been studied.All-Union Scientific-Research Institute of the Genetics and Breeding of Industrial Microorganisms, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 373–379, May–June, 1978.     

Molecular structure of the boron(III) oxide molecule in the SCF approximation

The potential surface for the boron(III) oxide (B₂O₃) ground state has been calculated in restricted HF approximation with a minimal STO—3G basis set. The equilibrium geometry has C_2v symmetry; the corresponding structural parameters are as follows: r(O_i—B₁)= 1.241 Å; r(B_i—O)= 1.341 Å ; ∠B₁QB₂ = 142° and ǒO₁B₁O = 177°. Calculations were also carried out using the SCF-Xα approach for two configurations of B₂O₃ with C_2v and D_∞h symmetry.     

Successive partitioning technique and Feenberg perturbation theory

Successive partitioning technique, when based on a modified bordering method for solving a system of linear equations and a relation for the inverse of a partitioned matrix leads to Feenberg's perturbation theory. This sheds light on the properties of the expansion, its bracketing properties and the nature of the “counting operators” used sometimes in this connection.     

Crystal and molecular structure of nitraminotetrazole and nitramino-1,2,4-triazole. IV. 5-nitraminotetrazole sodium salt sesquihydrate

The structure of 5-nitraminotetrazole sodium salt sesquihydrate was determined by X-ray diffraction. The crystals are monoclinic, space group P2₁/c;a = 3.551(1) Å, b = 21.834(4) Å, c = 9.075(2) Å; = 110.68(3)°; V = 658.3(2) ų; Z = 4; _calc = 1.807 g/cm³. The anion is planar and has an intramolecular hydrogen bond. The negative charge of the anion is localized on one of the oxygens of the nitro group. The sodium cation (c.n.6) is coordinated by three oxygen atoms of different anions and three oxygens of crystallization water. One of the crystallization water molecules is disordered in the unit cell. The anions are hydrogen-bonded with each other and with crystallization water molecules.Original Russian Text Copyright © 2004 by A. M. Astakhov, A. D. Vasiliev, M. S. Molokeev, L. A. Kruglyakova, A. M. Sirotinin, and R. S. StepanovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 562–565, May–June 2004.     

Nonempirical estimation of the ionization conditions of water and amorphous ice

Based on the results of nonempirical dynamics simulations of the vibrationally excited water clusters combined with the data on the dynamic reorganization of water cations obtained upon the vertical ionization of neutral clusters at the additional assumptions about the general rigidity of the hydrogen-bond fragments in amorphous ice and the thermal excitation of rotational vibrations and swinging motions of molecules in liquid water, the characteristic times of structure reorganization are estimated. The possibility to evaluate the photoelectric threshold of amorphous ice from the data about the adiabatic ionization of small water clusters, whose structure reorganization upon the electron removal does not involve opening of rings and formation of chains, is founded. It is shown that the conditions of the threshold ionization of liquid water can be judged from the second intermediate ionization potentials of neutral clusters, that is, from the potentials corresponding to the appearance of cations in which H₃O and OH fragments are separated with one water molecule. Based on an analysis of the electron density distribution in the cationic and neutral water clusters, a functional dependence of the ionization potentials on the number of water molecules is derived. Approximations of the calculated full adiabatic and intermediate ionization potentials of clusters comprising up to 12 water molecules provided the photoelectric threshold estimates of water and amorphous ice in close agreement with experiments.     

Chemical modification as a method of studying the functional groups of carboxylic proteinases

A review of the literature on the chemical modification of the functional groups of carboxylic proteinases is given. The following branches of the subject are considered: spatial organization and the modification of carboxy groups and amino groups of arginine, histidine, tyrosine, tryptophan, methionine, cystine, and cysteine residues. Chemical modification is considered as a method of studying the functional groups of enzymes which, in association with the results of x-ray structural analysis, permits an idea to be obtained of the mechanism of the action of carboxylic proteinases. V. M. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 591–607, September–October, 1980.     

Affinity chromatography of carboxylic proteinases on a polymeric sorbent containing gramicidin-C as ligand

A new polymeric sorbent for proteinases has been synthesized by the radical copolymerization of N-vinylpyrrolidone, bis-N-acryloylgramicidin C, and N,N-methylenebisacrylamide. Biospecific chromatography on the new sorbent has enabled an industrial preparation of procine pepsin to be purified by a factor of 2.5. With the aid of the new sorbent, a carboxylic proteinase has been isolated from the industrial preparation Tsellolignorin with a 15-fold purification factor.M. V. Lomonosov State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 215–218, March–April, 1986.