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351.
An attempt has been made for using MSA‐modified electrodes as linkage monolayers for electrostatic and covalent binding of cytochrome c (Cc). For MSA monolayers grown from an aqueous solution on Ag, attachment of Cc in its native state is proved in the case of covalent bonding. Electrostatic immobilization of Cc at pH 7 results in presence of at least some amount of Fe2+ high‐spin configuration and/or Fe3+ oxidation state. Native protein Fe2+ low‐spin state of Cc is observed after applying a negative potential to the Ag electrode. The influence of the solvent used for the preparation of the MSA monolayer and thiol surface coverage of the Ag surface was studied. It was shown that the key factor to obtain the native structure of Cc is the successful blocking of the metal surface by the MSA linking layer. IRRAS measurements of MSA on monocrystalline gold (111) at neutral pH confirm the successful electrostatic Cc immobilization, which preserves the Fe2+ oxidation state of the chromophore on this substrate. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
352.
In this paper we examine various types filters that appear in the context of continuous relations, pseudo-uniform spaces and pseudotopological spaces. There arise compactoid, precompact, totally bounded, bounded and other filters. We study their properties and relationships among them. 相似文献
353.
Zurek Jolanta Bowman Anna L. Sokalski W. Andrzej Mulholland Adrian J. 《Structural chemistry》2004,15(5):405-414
Aminoacyl-tRNA synthetases are centrally important enzymes in protein synthesis. We have investigated threonyl-tRNA synthetase from E. coli, complexed with reactants, using molecular mechanics and combined quantum mechanical/molecular mechanical (QM/MM) techniques. These modeling methods have the potential to provide molecular level understanding of enzyme catalytic processes. Modeling of this enzyme presents a number of challenges. The procedure of system preparation and testing is described in detail. For example, the number of metal ions at the active site, and their positions, were investigated. Molecular dynamics simulations suggest that the system is most stable when it contains only one magnesium ion, and the zinc ion is removed. Two different QM/MM methods were tested in models based on the findings of MM molecular dynamics simulations. AM1/CHARMM calculations resulted in unrealistic structures for the phosphates in this system. This is apparently due to an error of AM1. PM3/CHARMM calculations proved to be more suitable for this enzyme system. These results will provide a useful basis for future modeling investigations of the enzyme mechanism and dynamics. 相似文献
354.
JPC – Journal of Planar Chromatography – Modern TLC - The lipophilicity of thirty-seven N-[(4-arylpiperazin-1-yl)alkyl]-2- azaspiro[4.4]nonane- and [4.5]decane-1,3-dione derivatives has... 相似文献
355.
Karol Bula Teofil Jesionowski Andrzej Krysztafkiewicz Jolanta Janik 《Colloid and polymer science》2007,285(11):1267-1273
Dispersion and distribution of nanosized precipitated amorphous silica particles in poly(ethylene terephthalate) PET and poly(butylene
terephthalate) PBT matrices have been studied. The effect of silane coupling agent as well as processing conditions has been
analysed on the basis of microscopic analysis of sample morphology. N-2-(aminoethyl)-3-aminopropyltrimethoxysilane (A-1120) has been used as a silica surface modifier. The effect of the extrusion
process performance with a single and a twin screw extruder has been tested. It has been found that the processing conditions
are more important factors determining fine dispersion and homogenous distributions of filler particles in the matrix than
the filler surface modification. The results obtained have revealed that single screw extrusion is preferred only for processing
the composites comprising the silica modified with aminosilane, while the application of twin screw extrusion leads to homogenous
dispersion and fully deagglomeration of filler particles without silane treatment. It has been established that when the concentration
of silica filler increased from 3 up to 7% by weight, the secondary process of particle aggregation occurs. 相似文献
356.
Vytautas Getautis Albina Stanisauskaite Tadas Malinauskas Jolanta Stumbraite Valentas Gaidelis Vygintas Jankauskas 《Monatshefte für Chemie / Chemical Monthly》2006,137(11):1401-1409
Summary. Hydrazones containing 1-phenyl-1,2,3,4-tetrahydroquinoline units were synthesized starting from diphenylamine. These compounds
were found to constitute novel hole transporting materials and were characterized by the time of flight method. The hole drift
mobility in these compounds exceeds 10−6 cm2 V−1 s−1 at an electric field of 106 V cm−1. 相似文献
357.
Almantas Danilevicius Justina Dobiliene Christoph Wutz Jolanta Liesiene 《Cellulose (London, England)》2007,14(4):321-329
A new amphiphilic cellulose derivative phenoxyhydroxypropylhydroxyethylcellulose of substitution degree up to 0.67 was synthesized
by reaction of water-soluble hydroxyethylcellulose with 2,3-epoxypropylphenylether in the presence of sodium hydroxide as
a catalyst. The chemical composition of the derivative was confirmed by means of UV, IR- and 13C-NMR-spectroscopy. The derivatives with substitution degree up to 0.12 are soluble in water and water–alcohol mixtures. With
increasing substitution degree, the polymers lose their water solubility, but still dissolve in water–alcohol mixtures. All
products are soluble in aprotic solvents. The effect of the reaction conditions, such as temperature and molar ratios of reaction
components, on both the reaction rate and degree of substitution was investigated. 相似文献
358.
Javier Blasco Jolanta Stankiewicz Joaquín García 《Journal of solid state chemistry》2006,179(3):898-908
Gd1−xSrxFeO3−δ ferrites have been studied by means of X-ray powder diffraction in the whole composition range. Single-phase solid solution is found for x<0.09 and for x>0.63. At intermediate Sr content, phase segregation takes place. Compounds with x?0.05 crystallize in the orthorhombic structure, space group Pbnm. Oxygen-deficient Gd1−xSrxFeO3−δ with x?2/3 are cubic or nearly cubic. The oxygen vacancies stabilize the cubic phase for x=2/3 whereas highly oxidized samples show an orthorhombic distortion, which has not been observed earlier. Magnetic and electrical properties have been measured for the single-phase solid solutions. Gd1−xSrxFeO3−δ compounds with x?2/3 order antiferromagnetically below ∼100 K. In the paramagnetic region, their susceptibility follows the Curie-Weiss law in all but SrFeO2.96 compound. These ferrites show semiconducting behavior in the electrical transport likely related to atomic disorder. We find that the conductivity activation energy becomes larger by increasing either the Gd content or the oxygen vacancies. 相似文献
359.
Cezary A. Kozlowski Tomasz Girek WladysŁaw Walkowiak Jolanta Kozlowska 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(1-2):71-77
β-Cyclodextrin (β-CD) polymers were prepared by cross-linking of β-CD with phtalic and 3-nitrophtalic anhydride in anhydrous N,N-dimethylformamide (DMF) in the presence of NaH. The weight-average molecular weight (M
W) and the chemical structure of the polymers were determined using high performance size exclusion chromatography (HPSEC) with refractive index (RI) detector, and 1H NMR spectroscopy. The molecular weight of the polymer increased with molar ratio of substrates and reaction temperature. 1H NMR spectra revealed that the β-CD polymers contained both mono- and diesters of phtalic and 3-nitrophtalic acids. In the case of phtalic moieties about four or five diester moieties groups and for 3-nitrophtalic moieties about to or three diester moieties are linkages for β-CD molecule, respectively. Results of copper(II) flotation obtained with the use of nonylphenol polyoxyethyl glycol ether as an non-anionic surfactant and β-CD polymers as complexation collector agent, show␣that the removal of Cu2+ decreases with increase of molecular mass of β-CD polymers linked by phtalic or␣3-nitrophtalic anhydrides. For both derivatives with pH increase the copper(II) removal increase. The highest flotation removal, i.e. 93%, was found for β-CD polymers synthesized at 100 °C with molar ratio CD:NaH:3-nitrophtalic anhydride equal to 1:7:7. 相似文献
360.
Phenoxyacetic acid distribution in two-phase systems n-aliphatic hydrocarbon (C5–C8) – water and its dimerization in organic phase were investigated. The values of distribution coefficient (D
HR), distribution constant (K
D), and dimerization constant (K
dim) of acid were obtained. The empirical correlations of these quantities with Hildebrand solubility parameter of organic solvents were established. The influence of pH of the aqueous phase as well as the polarity of the applied organic solvents on phenoxyacetic acid physical chemistry in
the two-phase systems was described. 相似文献