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41.
Kinga Wzgarda-Raj Agnieszka J. Rybarczyk-Pirek Sawomir Wojtulewski Marcin Palusiak 《Acta Crystallographica. Section C, Structural Chemistry》2022,78(1):7-13
The structures of novel cocrystals of 4-nitropyridine N-oxide with benzenesulfonamide derivatives, namely, 4-nitrobenzenesulfonamide–4-nitropyridine N-oxide (1/1), C5H4N2O3·C6H6N2O4S, and 4-chlorobenzenesulfonamide–4-nitropyridine N-oxide (1/1), C6H6ClNO2S·C5H4N2O3, are stabilized by N—H…O hydrogen bonds, with the sulfonamide group acting as a proton donor. The O atoms of the N-oxide and nitro groups are acceptors in these interactions. The latter is a double acceptor of bifurcated hydrogen bonds. Previous studies on similar crystal structures indicated competition between these functional groups in the formation of hydrogen bonds, with the priority being for the N-oxide group. In contrast, the present X-ray studies indicate the existence of a hydrogen-bonding synthon including N—H…O(N-oxide) and N—H…O(nitro) bridges. We present here a more detailed analysis of the N-oxide–sulfonamide–nitro N—H…O ternary complex with quantum theory computations and the Quantum Theory of Atoms in Molecules (QTAIM) approach. Both interactions are present in the crystals, but the O atom of the N-oxide group is found to be a more effective proton acceptor in hydrogen bonds, with an interaction energy about twice that of the nitro-group O atoms. 相似文献
42.
Kinga Zr Roberto Ortiz Ebru Saatci Ronald Bardsley Tim Parr Elisabeth Csregi Mihaela Nistor 《Bioelectrochemistry (Amsterdam, Netherlands)》2009,76(1-2):93
An immunological capacitive biosensor for calpastatin was developed, optimized and applied for the analysis of meat extract samples. Anti-calpastatin antibody was immobilized on a gold electrode modified with a self-assembled monolayer of mercaptoundecanoic acid and Protein A from Staphylococcus aureus, and the obtained immunosensor was inserted as the working electrode in an electrochemical cell of a flow injection system. The dynamic range of the sensor was 20 to 160 ng/mL calpastatin. The electrode could be regenerated and re-used for more than 7 days with minimal reduction in sensitivity. For the analysis of real samples, the target analyte was extracted from the Longissimus dorsi muscle from beef carcasses directly after slaughtering. The extract was analyzed both with the developed immunosensor and microtiter plate ELISA, and a good correlation was obtained. However the immunosensor offers advantages of speed, simplicity, sensitivity and possibility for miniaturization over conventional assays for calpastatin quantification. 相似文献
43.
Kepczyński M Nawalany K Jachimska B Romek M Nowakowska M 《Colloids and surfaces. B, Biointerfaces》2006,49(1):22-30
A system of poly(ethylene glycol) bound tetraarylporphyrin entrapped in liposomal membranes was investigated. The interactions between the 5-(4-hydroxymethylphenyl)-10,15,20-tritolylporphyrin (Po) covalently attached to the poly(ethylene glycol) chain (PEG-Po), and phosphatidylcholine liposomes in the aqueous solution were studied. The adsorption of the investigated polymer to lipid vesicles was confirmed by measurements of dynamic light scattering and zeta potential. Experimental results demonstrate that the diameter of liposomes increased and the absolute value of the zeta potential decreased after addition of PEG-Po. The binding constants (K(b)) of Po chromophores to liposome in pH range from 5.2 to 9.0 were determined using fluorescence spectroscopy. The degree of binding was found to be pH-independent and the average value was 24.6 +/- 0.9 mg ml(-1). The acid-base properties of the porphyrin chromophores and their aggregation in an aqueous solution were also studied. pK values associated with imine-N protonation of the porphyrin core were found to be 2.59 and 0.68 at the ionic strength of 0.1 M. The equilibrium constant for dimerization, K(D), was found to be 5 x 10(3) M(-1). 相似文献
44.
Haubner K Tarábek J Ziegs F Lukeš V Jaehne E Dunsch L 《The journal of physical chemistry. A》2010,114(43):11545-11551
The influence of the molecular structure on the stabilization of charged states was studied in detail by in situ ESR UV-vis NIR spectroelectrochemistry at a novel α,ω-dicyano substituted β,β'-dibutylquaterthiophene (DCNDBQT) and the electrochemically generated cation and anion radicals have been proved for the first time. The voltammetry of DCNDBQT results in two separate oxidation steps with the reversible first one. The experimental absorption maxima at 646 and 1052 nm together with the calculated ones (by DFT method) as well as an ESR signal at the first anodic step prove the presence of a radical cation. Three additional optical bands (554, 906, and 1294 nm for CT-transition) can be attributed to the formation of cation radical dimer. The dicationic structure formed in the second oxidation step is not stable. The stabilization proceeds via a dimer formation in two chemical follow-up reactions. The existence of the dimeric structures was proved by ex situ MALDI TOF mass spectrometry. As the substitution by cyano groups opens the route to cathodic reductions, DCNDBQT shows a single quasi-reversible reduction step. Here, the in situ ESR UV-vis NIR spectroelectrochemical measurements and theoretical calculations let us confirm the electrochemical generation of an anion radical. As we found a low number of anion radicals by quantitative ESR spectroelectrochemistry and an appearance of additional bands in the UV-vis NIR absorption spectra, the formation of dimeric structures must be considered and was corroborated by mass spectrometry. The role of dimerization in the reaction mechanism of the DCNDBQT oxidation and reduction are discussed in general. The experimental results were interpreted using the quantum chemical calculations based on density functional theory. 相似文献
45.
Stanisław Boryczka Kinga Suwińska Georges Le Guillanton Quang Tho Do Driss Elothmani 《Journal of chemical crystallography》1998,28(7):555-560
The title compound (C14H11NO2) is monoclinic with a = 13.579(2), b = 5.297(1), c = 16.455(2) Å, = 98.11(2)°, Z = 4, and space group P21/n. The significant structural features lie in the two carbonyl groups of the glyoxamide which are oriented antiperiplanar to each other [–163.6(3)°]. The central bond C(1)–C(2) is 1.545(4) Å. The observed conformation is stabilized by intramolecular hydrogen bonds. 相似文献
46.
Andrzej Ziba Andrzej Malankiewicz Kinga Suwiska 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):o32-o33
The title compound, C6H7NS, is planar, with endo‐C—N—C bond angles of 118.7 (2) and 118.8 (2)°, and C—S bond lengths of 1.697 (2) and 1.692 (2) Å for the two symmetrically independent molecules. 1‐Methylpyridinium‐4‐thiolate is the major contributor to the molecular structure in the solid state. 相似文献
47.
Kinga Suwińska Janusz Lipkowski 《Journal of inclusion phenomena and macrocyclic chemistry》1988,6(3):237-248
The crystal structure of α-d-mannosido-benzo-18-crown-6·KSCN (1) was solved by X-ray single crystal diffractometry. C28H36O10·KSCN is orthorhombic, space groupP212121 withZ=4,a=8.035(4),b=9.960(2),c=38.83(2) Å,M r =629.8,V=3103.6 Å3,D x =1.347 g cm?3, μ(CuKα)=2.53 mm?1, λ=1.54178 Å,F(000)=1324. FinalR=0.043 for 1139 unique observed reflections measured at room temperature. The potassium ion is surrounded by a nearly planar hexagon of oxygen atoms of the macrocyclic ring and lies on the plane formed by those atoms. Hexagonal pyramidal coordination is completed by the nitrogen atom of the thiocyanate anion. The SCN ion was found on the face of the macrocyclic ring opposite that for the chiral mannopyranoside moiety. The molecular structure of α-d-mannosido-18-crown-6 (2) and the structure of molecular complexes of2 and α-d-glucosido-benzo-18-crown-6 (3) were studied by molecular mechanics methods. The results suggest enthalpy driven selectivity of complexation of the phenylalanine methyl ester (4) by2 and both enthalpy and entropy effects in selective complexation of4 by3. 相似文献
48.
The title compound (C22H18N2OS3) is monoclinic, with a=20.7446(5), b=8.332(1), c=24.393(7)°, β=112.12(1)° and space group P21/n. There are two independent molecules in the unit cell. Two quinoline moieties are nearly perpendicular to each other (76.9(1)°)
and (72.0(2)°). Both S-methylene fragments are trans-orientated with respect to the C(3)−S(1)−C(13) plane. Two pairs of sulfur
atoms in ortho-positions are in very close contact with sulfide preserving a skew conformation. The central 12-membered ring
adopts an unusual conformation.
Part XLIII in the series of Azinyl Sulfides. Part XLII: Maślankiewicz, M.J.; Maślankiewicz, A.J. Heterocycl. Chem.
1996,33, 1989. 相似文献
49.
Kinga Stolot 《Topology and its Applications》2006,153(18):3528-3545
We define an index of Conley type for a certain class of upper semicontinuous multivalued dynamical systems. We use the Szymczak functor and apply techniques introduced by Reineck, Mrozek and Srzednicki for the index over the base. Moreover we introduce the notion of the homotopy partial functor for the usc maps. We show that the index possesses Wa?ewski and homotopy properties. We also give four examples that exhibit the benefits of our index over the cohomological index defined by Mrozek and Kaczyński. 相似文献
50.