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Journal of Structural Chemistry

2011 year, number 6

1.
STRUCTURAL, electronIC PROPERTIES AND chemical BONDING IN protonated lithium metallates Li2-xÍxMO3 (M = Ti, Zr, Sn)

I. R. Shein, T. A. Denisova, Y. V. Baklanova, A. L. Ivanovskii
Keywords: lithium metallates Li2MO3 (M = Ti, Zr, Sn), protonation, structural, electronic properties, chemical bonding, ab initio calculations
Pages: 1081-1089

Abstract >>
Within density functional theory by an ab initio molecular dynamics method (SIESTA code) the features of structural, electronic properties and chemical bonding in lithium metallates Li2MO3 (M = Ti, Zr, Sn) are studied, as well as of their protonated forms Li2-xHxMO3 at all possible H+ → Li+ substitutions. With the use of the calculated crystal orbital overlap populations and the formation energies of Li2-xHxMO3 the most preferred H+ → Li+ substitutions in Li2MO3 metallates are discussed.



2.
STABILIZING HYDROGEN-HYDROGEN INTERACTIONS IN CATIONIC INDOPOLYCARBOCYANINE DYES

G. V. Baryshnikov, B. F. Minaev, V. A. Minaeva
Keywords: polymethine dyes, Bader method, functional density theory, bond critical point, binding energy, fluorescence quenching
Pages: 1090-1095

Abstract >>
A quantum chemical DFT method with the hybrid B3LYP functional in the 6-31G(d) basis set is employed to calculate the equilibrium geometric parameters of the ground and excited states of cationic symmetric indopolycarbocyanine dyes. Based on the Bader topological analysis of the electron density distribution function, it is found that there are hydrogen-hydrogen bonding interactions in the ground, first singlet, and first triplet states of the studied compounds. These interactions are assumed to have the dispersion character. The effect of the stabilization of the conformational position of methyl groups due to hydrogen-hydrogen interatomic interactions on fluorescence deactivation processes is shown. The total stabilization energy of hydrogen-hydrogen interatomic interactions in dye cations is found, which is ≈9 kcal/mol.



3.
COMPUTATIONAL INVESTIGATION OF THE CH3XC=S…S (X = H, HO, HS, PH2, CH3) BONDING TYPE

J.-Y. He1, Z.-W. Long1, J.-S. Zhang2
1 Laboratory for Photoelectric Technology and Application, Guizhou University Department of Physics, Guizhou University
2 College of Chemistry and Material Science, Guizhou Normal University
hjy_lxq@163.com, longshc@hotmail.com
Keywords: MP2, interaction energy, topological property analysis
Pages: 1096-1100

Abstract >>
The CH3XC=S…S (X = H, HO, HS, PH2, CH3) bonding types are investigated using the second order Møller-Plesset perturbation approximation with the cc-pVDZ basis set. Electrostatic density potential maps of CH3XC=S (X = H, HO, HS, PH2, CH3) are generated at the MP2/cc-pVDZ level of theory. The interaction energy and topological property are theoretically encompassed for the five complexes. Electrostatic density potential maps of five monomers are generated for the determination of attractive interaction sites. There are different misshaped electron clouds. The red-shifting character is obtained for the CH3XC=S…S (X = H, HO, HS, PH2) interaction. For all complexes the S…S bonds are typical closed-shell interactions, and the topological properties of the S…S bond fall short of three criteria for the existence of the hydrogen bond. Theoretical values are in very good agreement with the experimental results.



4.
PHASE FORMATION IN Li2MoO4-Rb2MoO4-MMoO4 (M = Ca, Sr, Ba, Pb) SYSTEMS AND THE CRYSTAL STRUCTURE OF α-Rb2Pb(MoO4)2

I. A. Gudkova, Z. A. Solodovnikova, S. F. Solodovnikov, E. S. Zolotova, N. V. Kuratieva
Keywords: lithium, rubidium, alkaline-earth metals, lead, binary molybdates, phase relations, solid solutions, crystal structure, palmierite
Pages: 1101-1107

Abstract >>
A subsolidus triangulation of Li2MoO4-Rb2MoO4-MMoO4 (M = Ca, Sr, Pb, Ba) systems is performed. The RbLiMoO4-Rb2M(MoO4)2 (M = Pb, Ba) joins, where 11 mol.% long Rb2M(MoO4)2-based solid solutions are found, are studied in most detail. Ternary molybdates do not form in the systems, which is confirmed by spontaneous flux crystallization. The α-Rb2Pb(MoO4)2 crystals are obtained and their crystal structure is solved (à = 20.9724(15) Å, b = 12.1261(8) Å, ñ = 16.1171(10) Å, β = 115.728(13)°, Ñ2/m space group, R = 0.0695, Z = 16), which is a monoclinic superstructure of the palmierite type and has the largest cell volume and the most complex structure among lead-containing palmierites. One of the MoO6 tetrahedra is orientationally disordered over two sites; lead atoms are shifted from the centers of their coordination polyhedra to one of their faces and have cn = 6-8; for rubidium cations cn = 10-12.



5.
CRYSTAL STRUCTURES OF TRIS-HEXAFLUORO- ACETYLACETONATES OF ALUMINUM AND SCANDIUM

A. I. Smolentsev, K. V. Zherikova, M. S. Trusov, P. A. Stabnikov, D. Y. Naumov, S. V. Borisov
Keywords: aluminum, scandium, ?-diketonates, single crystal X-ray crystallography, crystal chemistry
Pages: 1108-1115

Abstract >>
The structures of tris-hexafluoroacetylacetonates Al(hfa)3 and Sc(hfa)3·H2O are determined by single crystal X-ray crystallography (Bruker-Nonius X8 Apex diffractometer, MoKα radiation, T = 150(2) K). The Al(hfa)3 complex is trigonal, a = 17.8944(11) Å, c = 12.4061(11) Å, P-3ñ1 space group, V = 3440.3(4) Å3, Z = 6, R = 0.076. The Sc(hfa)3·H2O complex is monoclinic, a = 16.0926(4) Å, b = 14.7980(3) Å, c = 24.4020(5) Å, β = 125.641(1)°, P21/c space group, V = 4722.54(18) Å3, Z = 8, R = 0.060. The structures of the complexes are formed by neutral molecules; the coordination environment of the metal atom involves six oxygen atoms of three β-diketone ligands (Al(hfa)3) and, additionally, a water oxygen atom (Sc(hfa)3·H2O). The shortest Al…Al distance is 6.203(6) Å. The Sc(hfa)3·H2O molecules are joined in dimers by hydrogen bonds with Sc…Sc separations of 5.6992(8) Å and 5.6853(8) Å. In the crystals, the molecules are joined by van der Waals interactions, moreover, there are intermolecular contacts F…H ~ 2.5 Å in the structure of Sc(hfa)3·H2O.



6.
features of the structure formation of polymer COMPOSITES modified by A liquid lubricant

P. N. Petrova, A. A. Okhlopkova, A. L. Fedorov
Keywords: tribosystem, motor oil, polymer composites, structure, degree of crystallinity, strength, durability, wear inhibitors
Pages: 1116-1122

Abstract >>
Structure formation processes in polytetrafluoroethylene under the action of liquid lubricant components and zeolite particles are considered. Based on the results of single crystal X-ray diffraction, electron and atomic force microscopic, chromato mass spectroscopic studies, the formation mechanisms of polymer composites, which were obtained by liquid phase filling with motor oils, are proposed.



7.
SINGLE CRYSTAL X-RAY STRUCTURE OF 2-[({[(4-METHYLPHENYL)SULFONYL]METHYL}AMINO)CARBONYL]-1,3-DIOXO- 2,3-DIHYDRO-1H-INDEN-2-YL 2-THIOPHENECARBOXYLATE

A. Ramazani1, A.R. Kazemizadeh1, K. ??lepokura2, T. Lis2
1 Research Laboratory of MCRs, Department of Chemistry, Zanjan Branch, Islamic Azad University
2 Faculty of Chemistry, University of Wrocław
aliramazani@yahoo.com
Keywords: Single crystal X-ray structure, ?-acyloxycarboxamide, multi-component reaction, Passerini reaction, indane-1, 2, 3-trione, tosylmethyl isocyanide, 2-thiophenecarboxylic acid
Pages: 1123-1128

Abstract >>
The title compound 2-[({[(4-methylphenyl)sulfonyl]methyl}amino)carbonyl]-1,3-dioxo-2,3-dihydro-1H-inden-2-yl 2-thiophenecarboxylate is synthesized and studied by the single crystal X-ray diffraction method. The structure of the product is confirmed by IR, 1H and 13C NMR spectroscopy, and mass spectrometry. The structure is solved in the C2/c monoclinic space group with a = 16.739(3), b = 11.087(3), c = 23.194(4) Å, β = 93.32(3)°, V = 4297.2(16) Å3, Z = 8, R1 = 0.033 and wR2 = 0.088.



8.
CRYSTAL STRUCTURES OF TWO NEW DINUCLEAR Ag(I) COMPLEXES CONSTRUCTED FROM 4,4′-BIPHENYLDICARBOXYLIC ACID AND N-CONTAINING LIGANDS

S.-F. Lou1, X. Zheng2, Y. Chen2, X.-Y. Qiu2
1 Department of Public Subject, Shangqiu Medical College
2 Department of Chemisry, Shangqiu Normal University
loushufang@yahoo.com.cn
Pages: 1129-1135



9.
Adsorption Energy of THe As atom On THE Pd(111) surface according to the density functional theory DATA

S. E. Malykhin, M. Y. Burylin, S. Y. Burylin, I. L. Zil'berberg
Keywords: electrothermal atomic absorption spectrometry, arsenic, palladium, matrix modifier, density functional theory, atomization energy
Pages: 1136-1139

Abstract >>
Density functional theory in the plane wave basis set is used to study As adsorption on the Pd(111) surface in order to determine the action of a palladium chemical modifier used in electrothermal atomic absorption spectrometry (ETAAS). The calculated heat of desorption of the arsenic atom is 435 kJ/mole, which corresponds to the activation energy of arsenic atomization of 439 kJ/mole (in the range of high temperatures T > 1828 K), obtained by ETAAS. Based on the calculated data, the action of the palladium modifier for the determination of As is assumed to be controlled by the process of chemisorption.



10.
IONIC MOBILITY, STRUCTURE, AND CONDUCTIVITY OF 45ZrF4-35BiF3-20CsF GLASS ACCORDING TO 19F NMR, IR, RAMAN, AND IMPEDANCE SPECTROSCOPY

V. Y. Kavun, E. I. Voit, S. L. Sinebryukhov, A. B. Podgorbunskii, O. V. Brovkina, E. B. Merkulov, V. K. Goncharuk
Keywords: bismuth fluorozirconate glasses, 19F NMR spectra, ionic mobility, IR, Raman spectroscopy, ionic conductivity
Pages: 1140-1142

Abstract >>
19F NMR, IR, Raman and impedance spectroscopy are used to study the ionic mobility, structure, and conductivity of 45ZrF4-35BiF3-20CsF bismuth fluorozirconate glass. With the increase in temperature from 150 K to 500 K the fluorine-containing groups pass from the rigid lattice to local movements (reorientations), and then to diffusion. According to the results of IR and Raman spectroscopy, the lattice of this glass consists of ZrF8 polyhedra linked by their vertices into chains. The glass has high ionic conductivity: σ ≈ 1.8×10-4 S/cm in a temperature range of 480-485 K.



11.
HYDRATION NUMBERS OF GLYCINE IN AN AQUEOUS UREA SOLUTION

V. P. Korolev, A. L. Serebryakova
Keywords: urea, glycine, aqueous solutions, partial volumes, hydration numbers
Pages: 1143-1147

Abstract >>
An analysis of the literature data on the partial molar volume of glycine in an aqueous urea solution at 298 K is performed. The mentioned value linearly increases with the increase in the urea concentration (wt.%). The hydration number of glycine decreases by a factor of 2 when passing from water to the saturated (20m) urea solution.



12.
Study ON Octanol-Water Partition Coefficients of Benzene Halides by Molecular Vertex Distance Index

L.M. Liao1, J.F. Li1, G.D. Lei2, B. Wang3
1 College of Resource and Environment Science, Neijiang Normal University College of Chemistry and Life Science, Neijiang Normal University
2 College of Resource and Environment Science, Neijiang Normal University
3 College of Chemistry and Life Science, Neijiang Normal University
wangbi05@126.com
Pages: 1148-1151



13.
CRYSTAL STRUCTURE OF NEW MELAMINE BRIDGED POLYMERIC COMPLEX OF COPPER(II)

G.M. Mamoor1, O. ??ahin2, U. K. Islam3, Ejaz3, O. B??y??kg??ng??r2
1 Department of Polymer Engineering, University of Engineering & Technology
2 Department of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University
3 Department of Chemistry, Materials Chemistry Laboratory, Government College University
mamoorgm@uet.edu.pk
Keywords: X-ray diffraction analysis, copper(II), carboxylate, melamine
Pages: 1152-1156

Abstract >>
The new co-crystal copper(II) melamine complex poly[bis(μ-methacrylato)μ-(1,3,5-triazine-2,4,6-triamine)], C19H26Cu2N6O8 (1) crystallizes in the triclinic P-1 space group with a = 8.9670(2) Å, b = 9.4108(2) Å, c = 15.4476(3) Å, α = 96.6090(10)°, β = 100.6270(9)°, γ = 95.5950(10)°. Each Cu(II) exhibits a pseudooctahedral geometry. Four coplanar carboxylate oxygen atoms coordinated to the Cu(II) ion define the basal plane, whereas the apical position is occupied by one nitrogen atom from the melamine ligand. Here, the carboxylato-bridged two dinuclear copper(II) complexes are linked through melamine giving a 1D alternating chain. The structure of 1 consists of a two-dimensional supramolecular layer constructed by intermolecular N-H…N hydrogen bonds of the melamine ligands from adjacent one-dimensional [Cu2(C4H5O2)4(C3H6N6)] chains.



14.
CRYSTAL STRUCTURE OF A COMPLEX OF NICKEL(ii) WITH 2-AMINO-4-IMINO-2-PENTENE

S. I. Dorovskikh, K. V. Zherikova, N. V. Kuratieva, N. B. Morozova
Keywords: nickel(II), ?-diimine, X-ray crystallography
Pages: 1157-1160

Abstract >>
The structure of a nickel(II) complex with 2-amino-4-iminopentane is determined by X-ray crystallography at 150 K. Crystal data for C10H18N4Ni are: a = 10.9802(3) Å, b = 13.5780(4) Å, c = 8.0935(2) Å, β = 107.304(1)°, space group P21/c, V = 1152.04(5) Å3, Z = 4, dx = 1.459 g/cm3, R = 0.0283. The structure is molecular; the metal atom is coordinated by four nitrogen atoms of two β-diimine ligands. The Ni-N distances in Ni(NacNac)2 fall within 1.8571-1.8623 Å. The molecules in the crystal are joined by only van der Waals interactions.



15.
STRUCTURE OF A NEW MOLECULAR RHENIUM CLUSTER COMPLEX: trans-{[Ni(NH3)5]2[Re6Se8(CN)4(OH)2]}·6H2O

A. V. Ermolaev, A. I. Smolentsev, Y. V. Mironov
Keywords: octahedral cluster, rhenium, nickel, crystal structure
Pages: 1161-1163

Abstract >>
Counter-diffusion of the aqueous solution of Cs2.75K1.25[Re6Se8(CN)4(OH)2] and a water-ammonia solution of NiCl2 afforded crystals of a rhenium cluster complex trans-{[Ni(NH3)5]2[Re6Se8(CN)4(OH)2]}·6H2O. The structure of the complex is determined by single crystal X-ray diffraction. In the structure, nickel atoms have an octahedral coordination environment involving nitrogen atoms of five NH3 ligands and one CN ligand of the cluster anion. The anion has two bridging CN ligands in the trans-positions.



16.
CRYSTAL STRUCTURE OF A TRINUCLEAR Zn(II) COMPLEX: [Zn3L2(μ1,1-N3)2I2] [L = 2-[(3-DIMETHYLAMINOPROPYLIMINO)METHYL]-6-ETHOXYPHENOLATE]

S.-F. Lou1, X. Zheng2, X.-Y. Qiu2
1 Department of Public Subject, Shangqiu Medical College
2 Department of Chemisry, Shangqiu Normal University
loushufang@yahoo.com.cn
Keywords: schiff base, azide, trinuclear, zinc, crystal structure
Pages: 1164-1167

Abstract >>
Reaction of zinc iodide, sodium azide and 2-[(3-dimethylaminopropylimino)methyl]-6-ethoxyphenol (HL) results in the formation of a trinuclear complex [Zn3L21,1-N3)2I2]. The complex is characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. The complex possesses crystallographic two-fold rotation axis symmetry and crystallizes in the monoclinic system, C2/c space group, a = 23.241(2) Å, b = 10.849(1) Å, c = 17.384(2) Å, β = 120.868(1)°, V = 3762.4(6) Å3, Z = 4. The molecule consists of two [ZnL(N3)I] units connected together by a central Zn atom. The terminal Zn atom is five-coordinated in a trigonal-bipyramidal geometry, and the central Zn atom is six-coordinated in an octahedral geometry. The Zn⋯Zn separation between the terminal and the central Zn atoms is 3.257(2) Å.



17.
CRYSTAL STRUCTURE OF N,N′-BIS-(2,5-DIMETHOXYBENZYLIDENE)-1,3-DIAMINOPROPANE

A.D. Khalaji1, K. Fejfarova2, M. Dusek2
1 Department of Chemistry, Faculty of Science, Golestan University
2 Institute of Physics of the ASCR, Na Slovance 2
alidkhalaji@yahoo.com
Keywords: X-ray diffraction, orthorhombic symmetry, Schiff base
Pages: 1168-1170

Abstract >>
The Schiff-base compound N,N′-Bis-(2,5-dimethoxybenzylidene)-1,3-diaminopropan, (2,5-MeO-ba)2pn, is synthesized and characterized by elemental analysis, FT-IR and 1H NMR spectroscopy. The crystal structure of (2,5-MeO-ba)2pn is determined by X-ray single crystal diffraction analysis. The X-ray diffraction analysis at 120 K reveals that (2,5-MeO-ba)2pn crystallizes in the orthorhombic system, Fdd2 space group with a = 29.339(9) Å, b = 29.4073(11) Å, c = 4.4524(2) Å, V = 3840.8(3) Å3, μ = 0.72 mm-1, and Z = 8.



18.
INTERMOLECULAR INTERACTIONS IN HETEROMOLECULAR CRYSTALS OF TETRAZINE DERIVATIVES WITH AZOLES

E. S. Salmina, G. L. Rusinov, P. A. Slepukhin, R. I. Ishmetova, S. G. Tolshchina, V. A. Potemkin, M. A. Grishina
Keywords: Heteromolecular crystal structures formed by symmetrically and unsymmetrically 3, 6-disubstituted tetrazine derivatives with NH donor azoles are investigated. The main crystal motifs and the intermolecular interactions responsible for their formation are
Pages: 1171-1175



19.
STRUCTURE OF WATER−GLYCINE SOLUTIONS IN SATURATED AND NEAR-SATURATED REGIONS ACCORDING TO COMPRESSIBILITY DATA

O. V. Grineva, E. V. Belyaeva
Keywords: structure of liquids, cooperative hydrogen bonds, aqueous solutions, glycine, compressibility
Pages: 1176-1180

Abstract >>
Ultrasonic velocity and density values are measured for aqueous solutions containing 2.00 mol.%, 4.00 mol.%, and 5.00 mol.% glycine in a temperature range of 15-65°C, 5.50 mol.% glycine (20-65°C), and 6.00 mol.% glycine (25-65°C). Adiabatic compressibilities (κS) and molar adiabatic compressibilities (ΚS) are calculated. The values of κS and ΚS decrease monotonically with an increase in glycine concentrations up to saturation at all the temperatures. The temperature dependences of κS and ΚS have minima that are typical of water and aqueous solutions; the positions of the minima depend on the glycine concentration. The temperature coefficients of the molar compressibility, ∂ΚS/∂T, change their signs from negative to positive at lower temperatures (by approximately 10 deg) than ∂κS/∂T.



20.
SPATIAL CORRELATIONS OF IONS IN NANOCLUSTERS OF AN AQUEOUS SOLUTION OF NaCl

A. V. Teplukhin
Keywords: water, NaCl solution, structure, polarization, computer simulation, Monte Carlo method
Pages: 1181-1188

Abstract >>
The Monte Carlo method is used to calculate the radial distribution functions (RDFs) of Na+Cl, Na+Na+ , and ClCl ion pairs in water clusters that differ both in composition and size. An analysis of the RDFs shows that like-charged ions can approach one another at extremely small distances (direct ion contact) without the participation of a third ion of the opposite sign. The Na+Na+ (interionic distance 3.5 Å) and ClCl (interionic distance 5.25 Å) ion pairs are most likely to form in very dilute solutions. The composition of ionic associates changes with increasing concentration of ions in the solution (it is indicated by the emergence of the RDF peak at 4.25 Å and its further growth with concentration and by a selective visual analysis of instantaneous cluster configurations) so that groups of three, five, etc. ions of the opposite sign bearing a net charge of 1+ or 1- appear.



21.
RELAXATION PROCESSES OF THE STRUCTURAL REARRANGEMENT OF CLUSTERS IN LIQUIDS: 1,2-ETHANEDIOL, 1,2-PROPANEDIOL, AND 1,2,6-HEXANETRIOL

T. M. Usacheva, V. I. Zhuravlev, N. V. Lifanova, V. K. Matveev
Keywords: diols, triols, dielectric relaxation spectra, relaxation processes, fluctuation processes, dipole moments of clusters
Pages: 1189-1196

Abstract >>
The dielectric relaxation spectra (DRS) of 1,2-ethanediol, 1,2-propanediol, and 1,2,6-gexanetriol are analyzed in terms of the Dissado-Hill (DH) model in a wide range of temperatures, with all parameters required for calculating the cluster dipole moments being determined within the DH molecular model itself. The dependence of the equilibrium and relaxation properties of DRS on the hydrocarbon radical length and the number of OH groups is studied. The dipole moments of the clusters are calculated. It is shown how the roles of the processes of intracluster rearrangement are redistributed due to the break of hydrogen bonds and fluctuation processes of synchronous exchange of molecules between the clusters.



22.
MOLECULAR CHARACTERISTICS AND ANTIOXIDANT ACTIVITY OF POLYETHYLENE GLYCOLS MODIFIED BY STERICALLY HINDERED PHENOLS

L. A. Dobrun, E. L. Kuzyakina, O. V. Rakitina, O. Y. Sergeeva, M. E. Mikhailova, N. S. Domnina, A. V. Lezov
Keywords: conjugate, antioxidant, dynamic light scattering, viscometry, aggregation, antiradical activity
Pages: 1197-1202

Abstract >>
Chemical modification of polyethylene glycols by antioxidants belonging to the class of sterically hindered phenols is used to obtain water-soluble conjugates differing in the structure of the joined antioxidant and molecular weight. The inclusion of hydrophobic end groups in polyethylene glycol molecules leads to a decrease in the lower critical mixing point of the solution as compared to the original polymer. Dilute solution viscometry and light scattering are used to determine the molecular-mass characteristics of the polymers and the hydrodynamic radii of single conjugate molecules. The mass fraction of single molecules in aqueous solutions of the conjugates is greater than 95%. The aggregates are micellar-type particles whose core is formed by the hydrophobic moieties of sterically hindered phenols. It is shown that the antiradical activity of the antioxidants 3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionic acid and 3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid, which are used for the modification, differs only slightly, whereas the activity of the relevant conjugates increases significantly.



23.
EFFECT OF NONELECTROLYTES ON THE GEL FORMATION PROCESS IN AQUEOUS SILVER CYSTEINE SOLUTIONS

M. M. Ovchinnikov, S. D. Khizhnyak, P. M. Pakhomov
Keywords: L-cysteine, silver nitrate, hydrogel, cluster, percolation, supramolecular structure
Pages: 1203-1207

Abstract >>
Electron microscopy and dynamic light scattering are used to investigate the structuring process of a supramolecular system based on the aqueous solutions of L-cysteine and silver nitrate diluted with liquid water-soluble nonelectrolytes. The gel formation mechanism is discussed.



24.
STRUCTURE FORMATION OF THE MIXED GELS OF ZIRCONIUM OXYHYDRATE AND SILICIC ACID PRODUCED WITH DIFFERENT SEQUENCING OF REAGENTS

V. V. Avdin, I. V. Krivtsov, A. A. Lymar, Y. V. Matveichuk
Keywords: zirconia gel, silica gel, mixed gels, sol-gel technique, inorganic polymers, structure formation processes, Si-O-Zr bonds
Pages: 1208-1215

Abstract >>
The physicochemical characteristics of single and mixed zirconia and silica gels produced by the sol-gel technique at different synthesis pH and sequence of introducing the reagents in the mother liquid are presented. As a result of comparing the data obtained by different research methods, it is found that in the mixed gels, irrespective of the synthesis technique, Si-O-Zr bonds are present. The introduction of a zirconium salt in the mother liquid containing a silicate salt leads to the preferred formation of zirconia gel granules of 20-30 nm in diameter enclosed in the matrix of silica gel. The inverse sequence of introducing the gel-forming components in the reaction mixture promotes the formation of large gel aggregates containing the particles of less that 10 nm and having a high degree of polymerization. Mixed gels of zirconium oxyhydrate and silicic acid have an order higher sorptive capacity for yttrium (III) and calcium cations, as compared to single silica gels and zirconia gels.



25.
STUDY OF THE POLYMER INTERACTION WITH A SURFACE BY ENTROPIC SAMPLING

A. A. Yurchenko, M. A. Antyukhova, P. N. Vorontsov-velyaminov
Keywords: molecular simulation, polymers, small systems, lattice models, free energy
Pages: 1216-1223

Abstract >>
By means of a variant of the Monte Carlo method (entropic sampling within the Wang-Landau algorithm) the models of the interaction of a neutral polymer with a flat surface are studied. The method yields distribution functions over the energy and the distance from the polymer to the surface. Based on these distributions, excess entropies of the systems and their thermal properties are calculated: internal energy, heat capacity, average radius of gyration, average chain end-to-end distance, and average distance from the polymer to the surface. Continuous and lattice models are considered.



26.
CONTACT ANGLES AS INDICATORS OF THE POLYMER SURFACE STRUCTURE

Y. G. Bogdanova, V. D. Dolzhikova, D. S. Tsvetkova, I. M. Karzov, A. Y. Alent'ev
Keywords: wetting, polymer surface structure, surface energy, free volume, adhesion, adsorption layers, surfactants
Pages: 1224-1231

Abstract >>
The capacities of the wetting method for the characterization of the surface structure of polymers and surfactant adsorption layers on polymer surfaces and also the determination of the energy characteristics of polymer surfaces at different interfaces, which are used to optimize the choice of polymers in the solution of actual practical problems, are demonstrated.



27.
Metallization OF DNA ON THE surface

A. O. Puchkova, P. A. Sokolov, N. A. Kasyanenko
Keywords: DNA fixation, nanowires, silver reduction, DNA templates, nanoelectronics, nanobiotechnologies, silicon, DNA metallization
Pages: 1231-1238

Abstract >>
A method to develop DNA fibrils with a length more than a few tens of micrometers, oriented in one direction on the n- and p-type silicon surface is described. A new simple and effective technique is proposed to produce silver nanowires by electrochemical reduction of silver ions bound to DNA using the obtained fibrils as a template, as a result of which DNA molecules fixed on the surface of the n-type silicon single crystal are uniformly covered by silver clusters with a size of about 30 nm. The proposed metallization procedure of DNA on the n-type silicon surface has an advantage in comparison with a similar one for macromolecules fixed on freshly cleaved mica, glass surface, and ð-type silicon. n-Type silicon is not only a substrate, but also a source of electrons for silver reduction. The absence of an additional chemical component (reducer) principally distinguishes the proposed method from the others currently known. Atomic force microscopic images of fixed DNA molecules and prepared nanowires are obtained.



28.
EFFECT OF THE oligopeptide length ON THE DNA condensation process IN aqueous-salt solutionS

B. A. Dribinskii, N. A. Kasyanenko
Keywords: DNA, condensation, oligopeptides, lysine
Pages: 1239-1245

Abstract >>
The methods of circular dichroism, ultraviolet spectrophotometry, dynamic light scattering, viscometry, dynamic birefringence, and atomic force microscopy are employed to study the conformational properties of the DNA molecule during its complexation with oligopeptides. Samples with ñ 2, 3, and 5 monomeric L-lysine residues are used. Experimental data evidence that in the diluted solutions (with a low ionic strength) of DNA with oligopeptides (with 3 and 5 monomeric units) the condensation of the macromolecule is observed at specific peptide concentrations. For the bipeptide the DNA condensation in the solution is not observed. In the DNA solutions with a high ionic strength (1 M NaCl), oligopeptides do not affect the macromolecule size.



29.
EFFECT OF caffeine on DNA conformational changes AFTER IN VITRO γ-irradiation

S. V. Paston, A. E. Tarasov
Keywords: caffeine, DNA, ? irradiation, radioprotectors, radiosensitizers, spectrîphotometric analysis, DNA secondary structure
Pages: 1246-1251

Abstract >>
The radioprotective action of caffeine upon γ irradiation of DNA solutions is demonstrated by means of low gradient viscometry, flow birefringence, atomic force microscopy and UV spectroscopy. In the presence of caffeine, a decrease in the radiation effect on the DNA coil size in the solution, in the number of double-stranded breaks and damaged nitrogen bases, and in the degree of radiation-induced denaturation is observed.



30.
FORMATION OF THE AGGREGATES OF ACTINOCIN DERIVATIVES CONTAINING 4′-BENZO-15-CROWN-5 RADICALS IN AMIDE GROUPS AND THEIR INTERACTION WITH A DNA MOLECULE

E. B. Moroshkina, O. B. Sedova, T. A. Urusova
Keywords: DNA, benzo-crown-containing derivatives of phenoxazone, spectrophotometry, circular dichroism, viscometry, intercalation, H-aggregates, J-aggregates
Pages: 1252-1258

Abstract >>
Methods of spectrophotometry, spectropolarimetry, and viscometry are used to study the self-organization in the solution of crown-containing actinocin derivative (I) exhibiting antitumor activity and the interaction of the formed aggregates with a DNA molecule. The presence of the 4′-benzo-15-crown-5 radical in the structure of the studied compound determines the observed differences in its complexation with Na+ and K+ ions. The process of aggregation in the presence of K+ ions is accompanied by a shift of the long-wave band in the absorption spectrum to short-wave (the formation of H type aggregates) or long-wave (the formation of J type aggregates) regions depending on the K+ ion concentration in the solution. In the presence of Na+ ions, regardless of their concentration in the solution, J type aggregates form. A scheme of complex formation and their mutual transformations with changes in the ionic composition of the medium is proposed. A study of the interaction of this compound with DNA shows that in the presence of K+ ions it binds to the DNA molecule in the form of monomers and/or dimers without producing large supramolecular aggregates. The H and J structures formed in K+-containing solutions of compound I are broken in the interaction with DNA. If a solution of compound I is added to a DNA solution containing Na+ ions, the J type aggregates are formed directly on the surface of the DNA molecule. At the same type, the J structures originally formed in the Na+-containing solution of compound I practically do not interact with DNA. A study of this system shows that the introduction of the crown group in the compound molecule with a heterocyclic chromophore provides the opportunity to affect its affinity and binding to the DNA molecule by means of the ionic composition of the medium.