Crystal structure of ribosomal protein L1 from the bacterium <Emphasis Type="Italic">Aquifex aeolicus</Emphasis>

The crystal structure of ribosomal protein L1 from the bacterium Aquifex aeolicus was solved by the molecular-replacement method and refined to R _cryst = 19.4% and R _free = 25.1% at 2.1 Å protein consists of two domains linked together by a flexible hinge region. In the structure under consideration, the domains are in close proximity and adopt a closed conformation. Earlier, this conformation has been found in the structure of protein L1 from the bacterium Thermus thermophilus, whereas the structures of archaeal L1 proteins and the structures of all L1 proteins in the RNA-bound form have an open conformation. The fact that a closed conformation was found in the structures of two L1 proteins which crystallize in different space groups and belong to different bacteria suggests that this conformation is a characteristic feature of L1 bacterial proteins in the free form.     

Unusual catalytic properties of nanostructured nickel films obtained by laser electrodispersion

Nanostructured nickel films deposited by laser electrodispersion onto a silicon (semiconducting) or thermally oxidized silicon (insulating) substrate show a remarkably high catalytic activity (of the order of 10³–10⁴ (mol product) (mol Ni)^?1 h^?1) in the isomerization of chlorinated hydrocarbons and olefin hydrogenation. The special properties of the laser-deposited films are likely due to the small size (2.5 nm), developed surface, and amorphism of the nickel particles, as well as to highly active, charged particles appearing on the insulating substrate. The latter result from thermal fluctuations of electrons between closely spaced particles. In a film deposited on silicon covered with a natural oxide layer, a significant role is also played by charge redistribution between the substrate and metal particles.     

Determination of the exposed surface area of V2O5 on a V2O5/Al2O3 catalyst

NH₃, NO and CO₂ were tested as adsorbates for selective determination of exposed surface area of V₂O₅ on a V₂O₅/Al₂O₃ catalyst. The most promising appears to be CO₂ which interacts with the support Al₂O₃ only.

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NH₃, NO CO₂ V₂O₅ V₂O₅/Al₂O₃. CO₂, Al₂O₃.

     

Supported complexes of cupric chloride with DMF as catalysts in the reaction of CCl4 withn-decane

The complex of cupric chloride with DMF immobilized on the surface of silica gel exhibits high catalytic activity in the reaction of tetrachloromethane withn-decane. The fact that the reaction is inhibited by phenols and oxygen implies that it occurs by a radical mechanism. The immobilized catalyst that contains copper atoms connected through chlorine bridges and organic donor ligands is the most effective. Presented at the First Moscow Workshop on Highly Organized Catalytic Systems. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1835–1838, October, 1997.     

Relaxation and dynamical characteristics of nematic liquid crystals

We study the volt-ampere, volt-farad, and magnetofarad characteristics of homeo-tropically oriented MBBA samples of different thicknesses. The characteristics are obtained for different rates of change of the displacement voltage. It is shown that the volt-farad and magnetofarad curves have an obvious threshold. Increase in the scan rate leads to a shift of the threshold in the volt-farad curves to the higher voltage region. The dynamical volt-ampere curves have regions where the variation of the current is nonmonotonic at small scan rates and have a sharp maximum for large rates. Comparison of the volt-ampere and volt-farad characteristics shows that the physical processes causing the threshold in the volt-farad curves and the features of the volt-ampere curves are related to one another. A discussion of the results is given.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 67–71, April, 1988.