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排序方式: 共有140条查询结果,搜索用时 11 毫秒
31.
J. Brzezinski Z. Czlonkowska-Kohutnicka B. Czarnecka A. Kornás-Calka 《European Polymer Journal》1973,9(8):733-738
Weight-average molecular weights for PDMS fractions were determined by light scattering and the Archibald method in the range of 3000–300,000; the [ν]-M? relationship for toluene, 25°, was found to be This relationship was compared with those previously used. No upward curvature of the linear relation, log , at lower molecular weights was observed. Over the whole range of molecular weights, the [ν]-values in toluene were higher than [ν]θ-values in bromocyclohexane at 28°. 相似文献
32.
Joanna Kurek Wadysaw Boczo Piotr Przybylski Bogumi Brzezinski 《Journal of Molecular Structure》2007,846(1-3):13-22
The colchicine complexes with Li+, Na+ and K+ cations have been synthesized and studied by ESI MS, 1H and 13C NMR, FT-IR and PM5 semiempirical methods. It has been shown that colchicine forms stable complexes of 1:1 stoichiometry with monovalent metal cations. For Li+ cations also formation of the 2:1 stoichiometry complexes has been detected. The most stable structures of the complexes are those in which the acetamide groups are involved in the coordination process. The structures of the colchicine complexes with Li+, Na+ and K+ cations are visualized and discussed in details. 相似文献
33.
The synthesis of phthalazin-1-ones 6, 7, 8 via the reaction of 3-hydroxyisoindolin-l-ones 3, 4, 5 with hydrazine hydrate is described. Starting compounds 3, 4, 5 were regiospecifically prepared upon the lithiation (n-BuLi) of the benzanilides 1 and subsequently the reaction of the dilithiated anilides 2 with methyl pyridinecarboxylates. 相似文献
34.
Grzegorz Bejcar Piotr Przybylski Monika Walkowiak Bogumil Brzezinski 《Journal of Molecular Structure》2007,830(1-3):72-77
A new hydrazone of gossypol with 3,6,9-trioxadecylhydrazine (GHTO) has been synthesised and its structure has been studied by 1H NMR, 13C NMR, FT-IR spectroscopy and PM5 semiempirical methods. The results have shown that the newly synthesised hydrazone exists in solution in the N-imine–N-imine tautomeric form, stabilized by several intramolecular hydrogen bonds among which the O7H N16 intramolecular hydrogen bond is the strongest. The structure of GHTO is visualized by the PM5 semiempirical calculations. 相似文献
35.
Łukasz Miądowicz Patryk Jasik Józef E. Sienkiewicz 《Central European Journal of Physics》2013,11(9):1115-1122
We present four promising schemes for photoassociative formation of KLi molecule in its ground electronic state. Analysis is based on newly calculated adiabatic potentials supported by transition dipole moments and Franck-Condon factors. 相似文献
36.
Dr. Anna Kamecka Prof. Andrzej Kapturkiewicz M.Sc. Patryk Wójcik Prof. Kinga Suwińska Dr. Joanna Masternak 《欧洲无机化学杂志》2023,26(33):e202300438
The paper deals with the synthesis of a series of cationic [Pt(ppz)2(N^N)]2+ complexes containing deprotonated 1-phenyl-1H-pyrazole as cyclometallating (C^N) ligands and α-diimines (N^N) in the form of water-soluble salts with OTf− (trifluoromethanesulfonate) counter ions. These complexes were obtained from cis-[Pt(ppz)2Cl2] through chloride ligands substitution with α-diimines. The complexes were identified by means of NMR spectroscopy and their molecular structures were confirmed by X-ray crystallography. The photophysical properties of these complexes were studied in detail. These complexes showed strong luminescence in MeOH/EtOH 1 : 1 glasses at 77 K but were almost non-emitting in MeCN solutions at room temperature. Their emission properties were compared to analogues IrIII complexes. 相似文献
37.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
38.
Lee HJ Svahn E Swanson JM Lepp H Voth GA Brzezinski P Gennis RB 《Journal of the American Chemical Society》2010,132(45):16225-16239
Cytochrome c oxidase (CytcO), the final electron acceptor in the respiratory chain, catalyzes the reduction of O(2) to H(2)O while simultaneously pumping protons across the inner mitochondrial or bacterial membrane to maintain a transmembrane electrochemical gradient that drives, for example, ATP synthesis. In this work mutations that were predicted to alter proton translocation and enzyme activity in preliminary computational studies are characterized with extensive experimental and computational analysis. The mutations were introduced in the D pathway, one of two proton-uptake pathways, in CytcO from Rhodobacter sphaeroides . Serine residues 200 and 201, which are hydrogen-bonded to crystallographically resolved water molecules halfway up the D pathway, were replaced by more bulky hydrophobic residues (Ser200Ile, Ser200Val/Ser201Val, and Ser200Val/Ser201Tyr) to query the effects of changing the local structure on enzyme activity as well as proton uptake, release, and intermediate transitions. In addition, the effects of these mutations on internal proton transfer were investigated by blocking proton uptake at the pathway entrance (Asp132Asn replacement in addition to the above-mentioned mutations). Even though the overall activities of all mutant CytcO's were lowered, both the Ser200Ile and Ser200Val/Ser201Val variants maintained the ability to pump protons. The lowered activities were shown to be due to slowed oxidation kinetics during the P(R) → F and F → O transitions (P(R) is the "peroxy" intermediate formed at the catalytic site upon reaction of the four-electron-reduced CytcO with O(2), F is the oxoferryl intermediate, and O is the fully oxidized CytcO). Furthermore, the P(R) → F transition is shown to be essentially pH independent up to pH 12 (i.e., the apparent pK(a) of Glu286 is increased from 9.4 by at least 3 pK(a) units) in the Ser200Val/Ser201Val mutant. Explicit simulations of proton transport in the mutated enzymes revealed that the solvation dynamics can cause intriguing energetic consequences and hence provide mechanistic insights that would never be detected in static structures or simulations of the system with fixed protonation states (i.e., lacking explicit proton transport). The results are discussed in terms of the proton-pumping mechanism of CytcO. 相似文献
39.
Non-charged intramolecular hydrogen bonds formed in 2-(α-pyridyl N-oxide)ethane sulphonic acid cause strong continuous absorption; thus, these hydrogen bonds are easily polarizable. A double minimum proton potential with a deeper well at the oxygen atom of the NO group is present in these hydrogen bonds. 相似文献
40.
Leboda R Charmas B Skubiszewska-Zieba J Chodorowski S Oleszczuk P Gun'ko VM Pokrovskiy VA 《Journal of colloid and interface science》2005,284(1):39-47
Natural bentonite spent in the process of plant oil bleaching was used as an initial material for preparation of carbon-mineral adsorbents. The spent bleaching earth was treated using four procedures: T (thermal treatment); H (hydrothermal treatment); C (thermal treatment with addition of CCl4 vapor); M (modification of porous structure). Raw bentonite, RB (raw bleaching earth), and carbon materials prepared using plant oil were compared. The physicochemical characteristics of the adsorbents were determined using different methods: nitrogen adsorption/desorption, XRD, TEM, and MS-TPD. Carbon-mineral adsorbents contain from 5.23 to 19.92% C (w/w) and carbon adsorbents include from 84.2 to 91.18% C (w/w). Parallel processes of organic substance carbonization, porous structure modification, sublimation or evaporation of metal chlorides, and removal of hydrogen chloride take place during pyrolysis of waste mineral materials in the CCl4 atmosphere. 相似文献