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1.
Dr. Sebastian Lars Müller Xinglong Zhou Dr. Peter Leonard Oxana Korzhenko Dr. Constantin Daniliuc Prof. Dr. Frank Seela 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(12):3077-3090
Silver-mediated α-dC–Ag+–β-dC hybrid base pairs decorated with 5-iodo- or 5-octadiynyl residues are well accommodated in duplex DNA. A strong Tm increase and favorable thermodynamic data for duplex DNA were observed after addition of silver ions. The phenomenon is particularly obvious when both nucleobases of the base pairs are functionalized. Neither the position of the base pair, nor the type of 5-substituent had a negative influence. On the contrary, functionalization of conventional silver-mediated β-dC–Ag+–β-dC homo base pairs showed a negative impact induced by the bulky substituents. To this end, cytosine modified 12-mer oligodeoxynucleotides were prepared by solid-phase synthesis employing new α-anomeric 2′-deoxycytidine phosphoramidites. A multigram scale synthesis was developed for 5-iodo-α-d -2′-deoxycytidine ( 1 ) employing the direct glycosylation of cytosine with Hoffer's α-d -halogenose followed by separation of anomeric DMT nucleosides. Regarding base-pair stability and functionalization silver-mediated α/β-dC hybrid base pairs were found to be superior to β/β-dC homo pairs. According to their extraordinary properties, they might find applications in DNA diagnostics, material science, or nanotechnology. 相似文献
2.
Hussain F Bassil BS Kortz U Kholdeeva OA Timofeeva MN de Oliveira P Keita B Nadjo L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(17):4733-4742
The dititanium-containing 19-tungstodiarsenate(III) [Ti(2)(OH)(2)As(2)W(19)O(67)(H(2)O)](8-) (1) has been synthesized and characterized by IR, TGA, elemental analysis, electrochemistry, and catalytic studies. Single-crystal X-ray analysis was carried out on Cs(8)[Ti(2)(OH)(2)As(2)W(19)O(67)(H(2)O)].2CsCl.12H(2)O (Cs-1), which crystallizes in the monoclinic system, space group P2(1)/m, with a=12.7764(19), b=19.425(3), c=18.149(3) A, beta=110.234(3) degrees, and Z=2. Polyanion 1 comprises two (B-alpha-As(III)W(9)O(33)) Keggin moieties linked through an octahedral {WO(5)(H(2)O)} fragment and two unprecedented square-pyramidal {TiO(4)(OH)} groups, leading to a sandwich-type structure with nominal C(2v) symmetry. Synthesis of 1 was accomplished by reaction of TiOSO(4) and K(14)[As(2)W(19)O(67)(H(2)O)] in a 2:1 molar ratio in aqueous, acidic medium (pH 2). Polyanion 1 could also be isolated as a tetra-n-butyl ammonium (TBA) salt, {(n-C(4)H(9))(4)N}(5)H(3)[Ti(2)(OH)(2)As(2)W(19)O(67)(H(2)O)] (TBA-1). TBA-1 was studied by cyclic voltammetry in acetonitrile (MeCN) solutions containing 0.1 M LiClO(4) and compared with the results obtained with Cs-1 in aqueous media. In MeCN, the Ti(IV) and W(VI) waves could not be separated distinctly. An important adsorption phenomenon on the glassy carbon working electrode was encountered both in cyclic voltammetry and in controlled potential electrolysis and was confirmed by Electrochemical Quartz Crystal Microbalance (EQCM) studies on a carbon film. TBA-1, dissolved in MeCN, reacts with H(2)O(2) to give peroxo complexes stable enough for characterization by UV-visible spectroscopy, cyclic voltammetry, and EQCM. TBA-1 shows high catalytic activity (TOF=11.3 h(-1)) in cyclohexene oxidation with aqueous H(2)O(2) producing products typical of a heterolytic oxidation mechanism. The stability of TBA-1 under turnover conditions was confirmed by using IR, UV-visible spectroscopy as well as cyclic voltammetry. 相似文献
3.
Javier S. Acevedo Cortez Thelma Serrano Lucy T. González Oxana V. Kharissova 《Journal of Dispersion Science and Technology》2019,40(6):884-891
Natural sorbent materials have practical advantages for the oil spill cleanup, whose advantages are their low-cost, feasibility for real-life applications and environmental adaptability. In this work, absorption capacity was determined for lyophilized aloe, nopal and agar and their composites with silica, Fe3O4/polysterene and multi-wall carbon nanotubes (MWCNTs). Freeze-drying was performed in order to preserve the structure and increase the internal volume of sorbents. The structures of lyophilized sorbents and composites were analyzed by scanning electron microscopy (SEM). SEM images for lyophilized sorbents show a tridimensional arrangement formed by plant-derived materials, which allows the oil absorption. The composites keep their tridimensional structure after freeze-drying and composite formation and exhibit coupling between both materials. Absorption capacity of aloe, nopal and agar are 9?g/g, 3?g/g, and 26?g/g, respectively without any pretreatment. Composites with Fe3O4/polysterene own capacities of 5.8?g/g, 2.8?g/g, and 14?g/g, respectively. Finally, for MWCNT composites, capacities are 7.8?g/g, 2.9?g/g and 23?g/g. A significant difference of adsorption capacity between lyophilized sorbents and composites is attributed to lyophilized materials absorbing oil, water and other compounds. Meanwhile, for composites the absorption is a more selective process, since the hydrophobization does not allow the absorption of water. 相似文献
4.
Olga V. Dorofeeva Inna N. Kolesnikova Ilya I. Marochkin Oxana N. Ryzhova 《Structural chemistry》2011,22(6):1303-1314
Gas-phase enthalpies of formation of 122 relatively large organic molecules with up to 15 non-hydrogen atoms have been calculated
at the Gaussian-4 (G4) level of theory using the atomization reaction procedure. The calculated values were compared with
experimental data published mainly last years. Particular attention has been given to nitro compounds and nitrogen, oxygen,
and sulfur containing heterocyclic compounds. The expected accumulation of systematic errors as the molecular size increases
was not observed with increasing the number of non-hydrogen atoms from 6 to 15. The largest mean absolute deviation between
experimental and G4 enthalpies of formation, 10.7 kJ/mol, was revealed for nitro compounds. All theoretical values for nitro
compounds were underestimated by 5–15 kJ/mol. The best agreement with experiment with mean absolute deviation of 4.5 kJ/mol
was observed for compounds which types were widely presented in the original test set of G4 method. The mean absolute deviations
for nitrogen heterocycles (6.8 kJ/mol) and oxygen and sulfur heterocycles (9.1 kJ/mol) are noticeably larger. Experimental
enthalpies of formation of four compounds (N,N-dinitromethanamine, 2,3,5,6-tetrachloronitrobenzene, 2-methyl-2H-tetrazole, and proline) were suggested to be unreliable from comparison with the G4 values calculated from atomization energies
and isodesmic reactions. 相似文献
5.
Oxana Nipruk Nikolay Chernorukov Natalya Zakharycheva Elena Kostrova 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(1):519-529
Uranyl silicates with formula MII(HSiUO6)2·6H2O (MII=Mn, Co, Ni, Cu, Zn) were investigated in aqueous solutions in the pH range of 0÷14. The pH interval was established where compounds preserve their composition and structure. It varies in the pH range of (3.5–4.0)÷(10.8–11.4) and depends on MII type. Out of this pH interval investigated uranyl silicates convert to the compounds of other composition and structure, such as amorphous silica, polyuranates and hydroxides of 3d-transition elements. The solubility of MII(HSiUO6)2·6H2O was determined, it’s value changes on the several orders of magnitude from 10?6 M in subalkali solutions to 10?3 M in acid and strongly alkaline media. Using obtained experimental data the solubility products and solubility curves of uranyl silicates were calculated by mathematical modeling. Also the speciation diagrams of uranium (VI), silicon (IV) and M (II) in solutions and solids were plotted. 相似文献
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Mikhail Nikolaevich Krakhalev Oxana Olegovna Prishchepa Vitaly Sergeevich Sutormin Victor Yakovlevich Zyryanov 《Liquid crystals》2017,44(2):355-363
The polymer dispersed nematic liquid crystal (LC) with the tilted surface anchoring has been studied. The droplet orientational structures with two point surface defects – boojums and the surface ring defect – are formed within the films. The director tilt angle α = 40° ± 4° at the droplet interface and LC surface anchoring strength Ws ~ 10–6 (J m?2) have been estimated. The bipolar axes within the studied droplets of oblate ellipsoidal form can be randomly oriented are oriented randomly relatively to the ellipsoid axes as opposed to the droplets with homeotropic and tangential anchoring. 相似文献
9.
Galzitskaya OV 《Current protein & peptide science》2010,11(7):523-537
The problem of protein self-organization is one of the most important problems of molecular biology nowadays. Despite the recent success in the understanding of general principles of protein folding, details of this process are yet to be elucidated. Moreover, the prediction of protein folding rates has its own practical value due to the fact that aggregation directly depends on the rate of protein folding. The time of folding has been calculated for 67 proteins with known experimental data at the point of thermodynamic equilibrium between unfolded and native states using a Monte Carlo model where each residue is considered to be either folded as in the native state or completely disordered. The times of folding for 67 proteins which reach the native state within the limit of 10(8) Monte Carlo steps are in a good correlation with the experimentally measured folding rate at the mid-transition point (the correlation coefficient is -0.82). Theoretical consideration of a capillarity model for the process of protein folding demonstrates that the difference in the folding rate for proteins sharing more spherical and less spherical folds is the result of differences in the conformational entropy due to a larger surface of the boundary between folded and unfolded phases in the transition state for proteins with more spherical fold. The capillarity model allows us to predict the folding rate at the same level of correlation as by Monte Carlo simulations. The calculated model entropy capacity (conformational entropy per residue divided by the average contact energy per residue) for 67 proteins correlates by about 78% with the experimentally measured folding rate at the mid-transition point. 相似文献
10.
Viktor F. Ivanov Oxana L. Gribkova Olga D. Omelchenko Alexander A. Nekrasov Vladimir A. Tverskoy Anatoly V. Vannikov 《Journal of Solid State Electrochemistry》2010,14(11):2011-2019
Various polyaniline (PANI) interpolymer complexes with polyacids in the form of molecular solutions were synthesized by chemical
oxidative polymerization of aniline in the presence of water-soluble poly-(2-acrylamido-2-methyl-1-propanesulfonic acid) (flexible
backbone), poly-p,p′-(2,2′-disulfoacid)-diphenylene-terephthalamide (t-PASA, rigid backbone), and their mixtures in different ratios. The complexes
were characterized by UV-Vis-near infrared spectroscopy in solutions; also, the films’ drop-casts from these solutions were
investigated by cyclic voltammetry, spectroelectrochemical, direct current (DC) conductivity, and atomic force microscopy
(AFM) measurements. It was shown that the nature of polyacid affects the shape of spectra and the dynamics of their changes.
The character of spectral changes during the matrix synthesis of PANI in the presence of mixtures of the rigid-chain and flexible-chain
matrixes and the study of spectral properties of the obtained PANI solutions demonstrates the existence of the rigid-matrix
domination effect in the process of formation of PANI interpolymer complexes. Spectral properties of the obtained PANI complexes
with the mixtures of flexible-chain and rigid-chain polyacids of different ratios (3:1, 1:1, 1:3, and 1:6) are very similar
to those ones for the complex with rigid-chain t-PASA. At the same time, there is a correlation between the electrical conductivity
and morphology of the films of PANI complexes and their composition, the conductivity passing through a minimum for the complexes
with the polyacid mixtures (6:1, 3:1, and 1:1). 相似文献