Vibrational spectra and structure of 4-amino-1H-quinazolin-2-one 3-oxide

On the basis of a study of the vibrational spectra in the solid state of the product of the reaction of 2-cyanophenyl isocyanate with hydroxylamine and its isotopic analogs (¹⁵N O and ¹⁵NH₂) it was demonstrated that the compound obtained has the 4-amino-1H-quinazolin-2-one 3-oxide structure.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 968–972, July, 1981.     

Structural investigations of <Emphasis Type="Italic">E. Coli</Emphasis> dihydrolipoamide dehydrogenase in solution: Small-angle X-ray scattering and molecular docking

Dihydrolipoamide dehydrogenase from Escherichia coli (LpD) is a bacterial enzyme that is involved in the central metabolism and shared in common between the pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes. In the crystal structure, E. coli LpD is known to exist as a dimer. The present work is focused on analyzing the solution structure of LpD by small-angle X-ray scattering, molecular docking, and analytical ultracentrifugation. It was shown that in solution LpD exists as an equilibrium mixture of a dimer and a tetramer. The presence of oligomeric forms is determined by the multifunctionality of LpD in the cell, in particular, the required stoichiometry in the complexes.     

DNA interaction with synthetic polymers in solution

DNA complexes with cationic polymers (polyvinylamine (PVA), polyallylamine (PAA), polydimethylaminoethylmethacrylate (PDMAEM), poly-(N,N,N-trimethylammonio)ethyl methacrylate chloride (PTMAEM), poly-l-lysine (PLL)) were investigated. It was shown that volume and persistent length of DNA do not change essentially at low cationic polymer concentration in a solution. DNA packaging in 0.005 M NaCl was observed at charge ratio N/P ≈ 1. Secondary DNA structure in complexes was not disrupted, and DNA was protected from protonation. The comparison between DNA packaging in complexes with polycations and DNA condensation induced by trivalent ions was made.     

Magnetic properties of a monocrystalline quasicrystal in the Al-Pd-Mn system

Magnetic susceptibility of a monocrystalline icosahedral Al_70.2Pd_21.3Mn_8.5 quasicrystal was measured over the temperature range from 4 to 1100 K. The susceptibility was found to include the temperature-independent diamagnetic contribution, the temperature-dependent Curie’s contribution, and the contribution from the Pauli paramagnetism of an electron system with energy gap. An analysis of the low-temperature susceptibility revealed the presence of about 0.008% of ions with magnetic moment 4µ_B in the quasicrystal at 4 K. It is assumed that the ions with uncompensated magnetic moments appear near the structural vacancies in the quasicrystal lattice. The energy gap between the valence and conduction bands is estimated at Δ=0.64 eV, and the effective mass of charge carriers is equal to approximately 70 electron masses.     

Estimation of the Density of the Self-Interacting Dark-Matter Component within a Clump with Allowance for Recombination

The model of dark matter featuring a component in the form of free particles and antiparticles (a, ā ) possessing self-interaction of the Coulomb type is considered. Darkmattermay form small-scale clumps where the annihilation of particles a and ā is enhanced. This annihilation may lead to observable effects (in cosmic rays, for example) and/or to the destruction of these clumps. However, there is an ambiguity in describing the annihilation (via recombination) of very slow particles, which may include a and ā in clumps. The effect of annihilation (in terms of the residual number of free particles a and ā in clumps) is estimated within two approaches (simplified quantum-mechanical and classical) at chosen parameter values.     

Water-soluble polymeric derivatives of β-cyclodextrin

On the basis of hydrophilic copolymers of N-vinylamides??N-vinylpyrrolidone and N-methyl-N-vinylacetamide??that contain carboxylic or activated ester groups, new polymeric ??-cyclodextrin derivatives are synthesized via polymer-analogous transformations. Their solubility in water depends on the content of ??-cyclodextrin and the types of hydrophilic and reactive comonomers.     

Effect of the size and structure factors on the magnetic susceptibility of nanoparticles of cadmium sulfide

The dependence of the Van Vleck component of the magnetic susceptibility of nanostructured cadmium sulfide CdS on the geometry and structure of CdS nanoparticles has been established by analyzing the data obtained from diffraction and magnetic measurements. It has been found that a decrease in the size of wurtzite CdS nanoparticles leads to an increase in the degree of distortion of the sp ³ orbitals (i.e., the degree of covalence), which reaches a limiting value for elongated particles with an average size of 9 nm. In particles with smaller sizes, the character of the orbital distortion sharply changes, and the Van Vleck contribution returns to the value typical of coarse-grained CdS. Nanoparticles less than 9 nm in size have a specific disordered close-packed structure and a centrosymmetric shape. The data obtained have made it possible to understand the reason of the dimensional phase transition from the crystalline state to a specific nanostate of cadmium sulfide.     

Elementary and multielementary representations of vectroids

We prove that every finitely represented vectroid is determined, up to an isomorphism, by its completed biordered set. Elementary and multielementary representations of such vectroids (which play a central role for biinvolutive posets) are described.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 11, pp. 1451–1477, November, 1995.The authors are indebted to P. Gabriel for discussions, in which the idea o f this paper emerged, and numerous remarks taken into account in the final version of the paper.This work was supported by the Foundation for Fundamental Research o f the Ukrainian State Committee on Science and Technology and the International Science Foundation (Grant No. U6E000).     

Spectroscopic investigation of structure transformation in wavellite

The Electron Spin Resonance of VO²⁺, and the Infrared and Nuclear Magnetic Resonance of protons were studied in wavellite. Interpretation of¹H NMR by shape function calculation allows us to determine the distribution of protons between molecular water, OH-groups, the three-spin magnetic configuration H₃O⁺ and to ascertain the characteristic distances between protons. The spin-Hamiltonian parameters, Fermi contact interaction parameters and dipolar hyperfine coupling parameterPK were calculated. Three types of VO₂₊ complexes were detected in wavellite. It is found that VO²⁺(1)- and VO²⁺(2)-centres disappear and a new VO²⁺(3)-centre appears during annealing. VO²⁺(1) is more stable than VO²⁺(2). The parameters of the VO²⁺(3) complex change in the process of annealing. The transformation of VO²⁺(1) is connected with the destruction of acidic H₃O⁺-groups, and the transformation of VO²⁺(2) correlates with the loss of weakly-bonded water molecules in the wavellite structure. ThePK parameter and Δg?Δg _⊥ ratio can be used as markers of disorder in the wavellite structure.