Nikola $$\overset{\lower0.5em\hbox{$\smash{\scriptscriptstyle\smile}$}}{l}$$ Andreevich Dubrovsky (On his 70th birthday)

Acoustical Physics -     

Crystallization and preliminary X-ray diffraction study of recombinant ribokinase from <Emphasis Type="Italic">Thermus Species</Emphasis> 2.9

Ribokinase from a thermophilic strain of Thermus species 2.9 belonging to the carbohydrate ribokinase family (EC 2.7.1.15) was isolated, purified, and crystallized. The crystallization conditions were found by the vapor-diffusion technique and were then optimized to apply the capillary counter-diffusion technique. The X-ray diffraction data set was collected from the crystals, which were grown by the counter-diffusion technique, at the SPring-8 synchrotron radiation facility to 2.87 Å resolution. The crystals belong to sp. gr. P12₁1 and have the following unit-cell parameters: a = 81.613 Å, b = 156.132 Å, c = 87.714 Å, α = γ = 90°, β = 103.819°. The X-ray diffraction data set is suitable for determining the three-dimensional structure of the protein by the molecular-replacement method.     

A parametric antenna for hydrophysical research on long-distance paths

This work considers the capabilities of a hydroacoustic antenna based on principles of nonlinear acoustics to perform hydrophysical studies on long-distance paths. The antenna is described and results from initial experiments at sea are reported. The antenna is installed at a depth of 40 m at the site of investigations by the Hydrophysical Institute, Abkhazia Academy of Sciences. At a pumping frequency of 20 kHz, it allows the medium to be probed in the 300–3000 Hz range of parametric radiation on long-distance routes. The sharp directional pattern (2° angular resolution) of the broadband parametric radiation ensures single-mode excitation of the marine waveguide throughout the frequency band. Generation of a specific signal by a parametric antenna provides conditions for using the frequency dispersion of the velocity of acoustic signal propagation in the marine waveguide to compress the signal as it travels along a long-distance path.     

Preparation of the Crystal Complex of Phosphopantetheine Adenylyltransferase from Mycobacterium tuberculosis with Coenzyme A and Investigation of Its Three-Dimensional Structure at 2.1-Å Resolution

Crystallography Reports - Recombinant phosphopantetheine adenylyltransferase from Mycobacterium tuberculosis (PPAT Mt), which was produced by a high-producing strain and purified to 99%, was used...     

In memory of Fedor Ivanovich Kryazhev (December 13, 1924–February 24, 2006)

Chronicle

In memory of Fedor Ivanovich Kryazhev (December 13, 1924–February 24, 2006)     

A study of the products of the reduction of the antibiotic reumycin (6-methylpyrimido [5,4-e][1,2,4]triazine-5,7-dione)

The structures of the products of the reduction of the antibiotic reumycin (I), which is a specific autooxidizable acceptor of reducing equivalents from certain flavin dehydrogenases of the respiratory chain of the mitochondria of yeast and animal tissues, have been established with the aid of physicochemical methods (UV, IR, and PMR spectroscopy and mass spectrometry). In the determination of the structures of five reduction products of reumycin effective use has been made of high-resolution mass spectrometry and a consideration of the spectra of metastable ions (the DADI technique). It has been shown that only the asym-triazine ring in the initial (I) undergoes reduction and ring-opening.All-Union Scientific-Research Institute of Antibiotics, Moscow Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 85–95, January–February, 1981.     

Diethylamine and triethylamine as sources of the dienophile component in the reverse azadiene synthesis with dimethylpyrimido[4,5-e]- and-[5,4-e]-1,2,4-triazinediones and 1,2,4,5-tetrazines

Diethylamine (DEA) and triethylamine (TEA) can function as sources for the two-carbon component in the reverse azadiene synthesis. Reaction of 5,7-dimethylpyrimido[4,5-e]-1,2,4-triazine-6,8-dione, 6,8-dimethylpyrimido-[5,4-e]-1,2,4-triazine-5,7-dione, or 1,2,4,5-tetrazine with an excess of DEA or TEA gives, respectively, the pyrido[2,3-d]pyrimidine-2,4-dione,pyrido[3,2-d]pyrimidine-2,4-dione, or pyridazine. The presence of an oxidant (atmospheric oxygen, MnO₂, or an electron-acceptor solvent) is required for the reaction to occur. Reaction of 5,7-dimethylpyrimido[4,5-e]-1,2,4-triazinedione with piperidine, morpholine, or under certain conditions DEA, results in opening of the triazine ring to give uracils with an amidine group in the 6-position.For preliminary communication, see [1, 2].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1545–1558, November, 1990.     

N-alkylation of substituted pyrazoles and pyrazolo[3,4-d]pyrimidines with dimethylformamide diethyl acetal or triethyl orthoformate

The N-alkylation of some substituted pyrazoles and pyrazolo[3,4-d]pyrimidines with dimethylformamide diethyl acetal or triethyl orthoformate has been examined. Dimethylformamide diethyl acetal is more effective as an alkylating agent than triethyl orthoformate. Alkylation of 3-methoxycarbonylpyrazole gives a mixture of N-1- and N-2-ethyl derivatives. Alkylation of pyrazolo[3,4-d]pyrimidines takes place at the 1-position of the pyrazole ring only. In the case of thio-derivatives of pyrazolo[3,4-d]pyrimidines, S-alkylation occurs in addition to N-alkylation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 914–919, July, 1988.     

Neutral injection complex for the Globus-M spherical tokamak

The method of neutral injection is studied as applied to small tokamaks, including those with a small aspect ratio. Devices having constituted the basis for a neutral injection complex of the Globus-M spherical tokamak are listed. The atomic beam injector and systems providing its functioning are described in detail. Techniques to measure the basic parameters of the beam that are used in the injector are outlined. The atomic beam parameters obtained using IPM-1 and IPM-2 ion sources during bench tests and during operation of the complex are presented. The range of the operating parameters of the neutral injection complex and ways of its expansion are discussed.