Three-Dimensional Structure of Recombinant Thermophilic Ribokinase from Thermus speсies 2.9 in Complex with Adenosine Diphosphate

Crystallography Reports - The three-dimensional structure of recombinant thermophilic ribokinase from Thermus speсies 2.9 was determined at 2.4 Å resolution using crystals, which were...     

Observation of nucleon clusters in the spontaneous decay of234U

The emission of Ne and Mg nuclei was detected in the spontaneous decay of²³⁴U with probabilities of, respectively, (3.9 ±1.0) × 10^?13 and (2.3 ±0.7) × 10^?13 relative toα-decay. The upper limits of this kind of decay for²³⁵U and²³⁶U have been established. Systematics of half-lives for cluster emission are found to be similar to the Geiger-Nuttall dependence forα-decay. Some evidence for the presence of hindrance to cluster emission from the odd-mass nuclei²³³U and²³⁵U is obtained.     

Regiochemistry of the addition of mercury salts to bornylene

The dependence of the regiochemistry of the mercuration of bornylene on the nature of the mercurating reagent and on the solvent has been found. The structures of the intermediate and transition state in these reactions have been proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 501–505, March, 1994.     

Reactions of mercury salts with benzo- and tetrafluorobenzobarrelenes

Regiochemistry and stereochemistry of the addition of mercury salts to benzobarrelene and tetrafluorobenzobarrelene have been studied in acetic acid and methanol. The effect of the substrate structure on the regiochemistry of the reaction is discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1105–1108, June, 1994.     

Recording and reading of intense optical pulses based on the induced transparency

The effect of spatial localization of the atomic (Raman) coherence in the forbidden transition of a three-level atom is studied for two intense optical pulses with comparable Rabi frequencies. We propose to use this effect for coherent recording of intense optical pulses. Various schemes of reading of the recorded pulse are considered.     

Decomposition of hexafluoropropylene oxide in a strong IR field

Multiphoton dissociation (MPD) of hexafluoropropylene oxide (HFPO) under focused CO₂-laser radiation was studied. A high-energy channel of HFPO decomposition was revealed. The dependences of the MPD yield and the ratio between various channels of HFPO decomposition on the laser radiation frequency in the range from 967.7 to 1090.0 cm^–1, the incident radiation energy, and the initial pressure of HFPO were obtained. A considerable contribution of thermal decomposition of HFPO occurring outside of the irradiated zone to the total yield of its decomposition was established. An explanation for the pressure dependence of the yield of HFPO decomposition was suggested.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2174–2180, November, 1995.The authors are grateful to the Russian Foundation for Basic Research for financial support of this work (Project No. 94-03-09059).     

Nuclear oxide fuel analysis

As a rule the analysis of nuclear oxide fuel includes the determination of uranium, plutonium, their isotopic composition, cation impurities, carbon, nitrogen, chlorine, fluorine, oxygen coefficient. In this paper we discuss different methods for the a analysis of unirradiated uranium and plutonium oxide fuelds used in the laboratories of the Analytical Chemistry Department: coulometry, emission analysis, chromatography, X-ray analysis. Much consideration is being given to the analysis of uranium and plutonium oxide samples and uranium-plutonium mixed fuels irradiated in the BOR-60 using mass-spectrometric (isotope dilution method) and radiometric techniques. The results of uranium and plutonium determination by these methods are compared. The main analytical characteristics of the methods are given.     

Kinetics and mechanism of azidomercuration of alkenes,cycloalkenes, and their derivatives with a mercuric acetate-sodium azide system

The kinetics of azidomercuration of alkenes, cycioalkenes, and their derivatives with a Hg(OAc)₂-NaN₃ system (1 1, 1 2, and 1 3) was studied. Based on the data on the product structure and kinetic results, it was concluded that HgOAcN₃ and Hg(N₃)₂ play the role of azidomercuration reagents. The reactions with alkenes having a strained double bond occur by a concerted scheme. With nonstrained alkenes, a multistep mechanism is realized, its first reversible step involving the formation of a mercurinium intermediate with an ion pair structure.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No.12, pp. 2479–2485, December, 1995.     

Salt effects in the mercuration of unsaturated compounds. Kinetic evidence for the formation of ion pairs and a solvated ion

The kinetics of mercuration of bornylene and cyclohexene in different solvents in the presence of NaOAc and LiClO₄ has been investigated. Addition of NaOAc sharply decreases the rate of addition reactions of mercuric acetate to bornylene and cyclohexene in alcohols; the main direction of the mercuration of bornylene is the formation of acetoxy-adducts, and the yield of solvo-adducts decreases from 76 % in the absence of NaOAc, to 19 % in the presence of the salt (4·10^–3 mol L^–1). A reaction scheme involving the participation of intermediate ion pairs and a solvated mercurinium ion is suggested and confirmed by a steady-state concentration method. The influence of NaOAc on the rate of the reaction and on product formation is realized through the common ion effect.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 819–826, May, 1994.