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1.
This paper presents a quantum chemical calculation of native (2–7 fructoside residues) and chemically modified (2–4 fructoside residues) levan molecule models. A levan modification was carried out by oxidation and the following reduction or hyrdazonation of the fructoside rings. The conformational particularity and reaction ability was studied for the native and for the modified levan molecules. 相似文献
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3.
Xingping Qiu Svetlana A. Sukhishvili 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):183-191
Free‐radical copolymerizations of N‐vinylcaprolactam (VCL) and glycidyl methacrylate (GMA) were investigated to synthesize temperature‐responsive reactive copolymers with minimized compositional heterogeneity. The average copolymer composition was determined by Fourier transform infrared and nuclear magnetic resonance techniques. The reactivity ratios for VCL and GMA were found to be 0.0365 ± 0.0009 and 6.44 ± 0.36 by the Fineman–Ross method and 0.039 ± 0.006 and 6.75 ± 0.29 by the Kelen–Tudos method, respectively. When prepared by batch polymerization, VCL–GMA copolymers had a highly heterogeneous composition and fractions of different solubilities in water. The use of a gradual feeding technique, which included the sequential addition of more reactive GMA monomer into the reaction, yielded copolymers with much more homogeneous composition. The produced copolymers with 0.9 and 0.11 fractional GMA contents preserved their temperature‐responsive properties and precipitated from aqueous solutions when the temperature exceeded 31 °C. The GMA units in the VCL–GMA copolymers were capable of reacting with amino end‐functionalized poly(ethylene oxide) at room temperature to produce poly(N‐vinylcaprolactam)–poly(ethylene oxide) graft copolymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 183–191, 2006 相似文献
4.
Mikhailov Oleg V. Kazymova Marina A. Shumilova Tatyana A. Solovieva Svetlana S. 《Transition Metal Chemistry》2003,28(6):665-667
The complexing processes in the triple copper(II)–thiocarbohydrazide–propanone system taking place in a copper(II) hexacyanoferrate(II) gelatin-immobilized matrix in contact with aqueous-alkaline solutions (pH12), containing thiocarbohydrazide and propanone, have been studied. Template synthesis leading to a macrocyclic coordination compound with the tetradentate N,N,S,S-donor ligand, (4,4,6-trimethyl-2,3,7,8-tetraazanonen-6-dithiohydrazide-1,9), occurs under these specific conditions when thiocarbohydrazide and propanone are the ligand synthons. 相似文献
5.
Timerbaev AR Aleksenko SS Polec-Pawlak K Ruzik R Semenova O Hartinger CG Oszwaldowski S Galanski M Jarosz M Keppler BK 《Electrophoresis》2004,25(13):1988-1995
Characterizing how platinum metallocomplexes bind to human serum albumin (HSA) is essential in evaluating anticancer drug candidates. Using cisplatin as a reference complex, the application of capillary electrophoresis (CE) to reliably assess drug/HSA interactions was validated. Since this complex is small compared to the size of the protein, the binding response could only be recognized when applying CE coupled to a (platinum) metal-specific mode of detection, namely inductively coupled plasma-mass spectrometry (ICP-MS). This coupling allowed for confirmation of a specific affinity of cisplatin and novel Pt complexes to HSA, measurement of the kinetics of binding reactions, and determination of the number of drug molecules attached to the protein. As the cisplatin/HSA molar ratio increased, the reaction rate became faster with a maximum on the kinetic curve appearing at about 50 h of incubation at 20 times excess of cisplatin. The reaction was characterized as a pseudo-first order reaction with the rate constant k = 0.003 min(-1) at 37 degrees C. When incubated with a 20-fold excess of cisplatin, HSA bound up to 10 mol of Pt per mol of the protein. This is indicative for a strong metal-protein coordination occurring at several HSA sites other than the only protein cysteine residue. Structural analogs of cisplatin, bearing aminoalcohol ligands, showed comparable protein binding reactivity and stoichiometry but a common equilibrium was not reached even after one week of incubation. Also apparent was a two-step mechanism of the binding reaction. Results demonstrated the suitability of CE-ICP-MS as a rapid assay for high-throughput studying of drug/HSA interactions. 相似文献
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Svetlana V. Amosova Vladimir A. Shagun Natalia A. Makhaeva Konstantin A. Lysenko 《Journal of organometallic chemistry》2007,692(16):3307-3315
The structure of 2,4-dibromo-2-dibromomethyl-3,3-dimethyl-1-selena-3-silacyclopentene-4, formed by regioselective electrophilic addition of SeBr4 to dimethyl diethynyl silane, has been determined using X-ray analysis technique. Quantum chemistry methods were used to study elementary stages of the reaction. It was found that the first stage consisted of SeBr4 conversion into bimolecular complex Br2?SeBr2, initiated by dimethyl diethynyl silane. Possible formation of five-membered and six-membered heterocycles involves different cyclization mechanisms. The formation of only five-membered heterocycle is explained by kinetically preferable ring closure through four-center transition state. The conclusions obtained by calculations were confirmed by monitoring of the reaction using 1H NMR method. 相似文献
8.
Ellis MJ Antonyuk SV Strange RW Sawers G Eady RR Hasnain SS 《Inorganic chemistry》2004,43(24):7591-7593
Copper nitrite reductases contain both an electron-transfer type 1 Cu site and a catalytic type 2 Cu site. We have mutated one of the type 2 copper ligating histidines to observe the effect on catalytic turnover. This mutation has created a unique site where Cu is ligated by 2 His Nepsilon2 atoms alone. 相似文献
9.
Oleg V. Mikhailov Marina A. Kazymova Tatyana A. Shumilova Galina A. Chmutova Svetlana E. Solovieva 《Transition Metal Chemistry》2005,30(3):299-304
The complexing process proceeding in the NiII–thiocarbohydrazide (H2N–H–NC(=S)–NH–NH2)–propanone triple system in EtOH solution and nickel(II)hexacyanoferrate(II) gelatin-immobilized matrix has been studied. It has been found that in the first case, template synthesis leading, as a minimum, to formation of three coordination compounds of NiII with (N,N,S,S)-donor tetradentate ligands having NiL1, NiL2 and NiL3compositions where L1 is 4,6,6-trimethyl-2,3,7,8-tetraazanonen-3-di(thiohydrazide)-1,9, L2 is 4,6,6,12-tetrametyl-1,9-dithio-2,3,7,8,10,11-hexaazatridekadien-3,11-hydrazide-1 and L3 is 2,8,10,10,16-pentamethyl-5,13-dithio-3,4,6,7,11,12,14,15-octaazaheptadekatrien-2,7,15 is observed, whereas in the gelatin-immobilized matrix, a complexing process in the system considered does not occur. 相似文献
10.
Svetlana B. Lyubchik Irene I. Perepichka Olga L. Galushko Andrey I. Lyubchik Elena S. Lygina Isabel M. Fonseca 《Adsorption》2005,11(5-6):581-593
In order to understand the patterns of the adsorption equilibrium of Cr (III) on activated carbon, the adsorption process
was studied by two different ways: classical batch experiments on commercial Norit and Merck activated carbons and their oxidized
forms in a wide range of pHs; and extended time-based tests at the same pH values on the same adsorbents. This approach allowed
us to understand the role of texture, chemical carbon surface functionality and experimental conditions (initial pH of the
solution, contact time and adsorbate/adsorbent ratio) on the effectiveness of Cr (III) removal. The adsorption process of
Cr (III) at (24 ± 1∘C) on Merck and Norit activated carbons and their oxidized forms were studied at pH values between 1.5 and 5 (either adjusted
or buffered). Chromium concentration was fixed at 200 ppm. The carbon loading ranged from 1.2 to 20 g/l. The carbon/Cr (III)
solution contact time was varied from 0.5–1 month to 5 months, to ensure that the saturation of the carbon level was reached.
According to the data obtained, the presence of carboxylic groups on carbon surface seems to enhance Cr (III) uptake at initial
pH of the solution in the range between 2 and 4. Depending on the nature of the adsorbent surface chemistry, the contact time
to reach equilibrium may range from 3 to 5 months. There is an optimum carbon loading which limits the Cr (III) uptake/removal
at given pH value. In order to understand the adsorption process, an ion exchange, surface complex and surface precipitation
were considered.
This paper was presented in the 5th Brazilian Meeting on Adsorption, held at Natal, Brazil, 18-21 July, 2004. 相似文献