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131.
132.
Glucose isomerase was immobilized by itself and coimmobilized with cellulase and β-glucosidase using a polyurethane foam (Hypol® FHP 2002). Approximately 50% of the enzyme added was immobilized. The immobilized enzyme was active at pH values as low as 6.8. When immobilized alone, the Km for Mg2+ increased by 5.5fold and the Km for fructose increased 62%. The half-life of the immobilized glucose isomerase was approximately 160 h of continuous hydrolysis, with a substantial (about 35–40%) amount of activity remaining even after 1000 h. When all three enzymes were immobilized together, the system was found capable of functioning at pH 7.0 to produce fructose from both soluble and insoluble cellulose substrates. At this pH, the glucose:fructose ratio was 70:30. The advantageous properties of the foam as a support for enzyme immobilization and the efficiency of the one-step conversion process outlined combine to make this system appear valuable for use in high fructose syrup production. 相似文献
133.
Designed azobenzene-based enediyne-amino acid C(2)-symmetric hybrids have been synthesized and the role of amino acid linker in stabilizing the Z form has been demonstrated; DNA-binding and cleavage studies have established higher reactivity of the Z-isomers. 相似文献
134.
Adaptive Markov Chain Monte Carlo (AMCMC) is a class of MCMC algorithms where the proposal distribution changes at every iteration of the chain. In this case it is important to verify that such a Markov Chain indeed has a stationary distribution. In this paper we discuss a diffusion approximation to a discrete time AMCMC. This diffusion approximation is different when compared to the diffusion approximation as in Gelman et al. [5] where the state space increases in dimension to ∞. In our approach the time parameter is sped up in such a way that the limiting process (as the mesh size goes to 0) approaches to a non-trivial diffusion process. 相似文献
135.
Mishael YG Dubin PL de Vries R Kayitmazer AB 《Langmuir : the ACS journal of surfaces and colloids》2007,23(5):2510-2516
The adsorption of quaternized poly(vinylpyridine) (QPVP) on controlled pore glass (CPG) size, over the ionic strength range 0.001-0.5 M was found to display nonmonotonic behavior as a function of pore size. Both adsorption kinetics and ionic strength effects deviated dramatically from behavior typical of adsorption on flat surfaces when the ratio of the pore radius Rp to the polymer hydrodynamic radius Rh became smaller than ca. 2. Ionic strength enhancement of adsorption for small pore sizes was observed at much higher salt concentrations than is typical for polycation adsorption on flat surfaces. The amount of polymer adsorbed per unit surface area of glass GammaA, in 0.5 M NaCl, exhibited a shallow maximum at Rp/Rh approximately 5. Since the value of GammaA for small pore size CPG is strongly depressed by the large surface area, an alternative and more interesting observation is that the amount of polymer adsorbed per gram of CPG, Gammaw, displays a strong maximum when Rp is equal to or slightly smaller than Rh. The efficiency with which QPVP binds anionic micelles to (negatively charged) CPG (grams of surfactant/grams of QPVP) increases strongly with diminishing pore size, indicating that the configuration of polycation bound to small pores favors micelle binding. Since the micelles are larger than small pores, the results indicate that when Rp < Rh, adsorbed polycation molecules reside only partially within the pore. The results of this study are supported by simulations of polyelectrolytes within cylindrical cavities. 相似文献
136.
Basak A Roy SK Das S Hazra AB Ghosh SC Jha S 《Chemical communications (Cambridge, England)》2007,(6):622-624
The spontaneous activation of a nonaromatic enediynyl azide under ambient conditions has been demonstrated. The aromatic enediyne followed the expected cycloaddition with the alkene in the neighbouring arm to form a stable bridged bicyclic enediyne. 相似文献
137.
Bispropargyl sulfones equipped with aromatic rings of dissimilar nature were synthesized. Under basic conditions, these sulfones isomerized to the bisallenic sulfones, creating a competitive scenario between two alternate Garratt-Braverman (GB) cyclization pathways. The observed product distribution ruled out the involvement of any ionic intermediate and supported the diradical mechanism with greater involvement of the electron-rich aromatic ring via the more nucleophilic radical. DFT-based calculations supported the diradical mechanism along with the observed selectivity. 相似文献
138.
Roy S Anoop A Biradha K Basak A 《Angewandte Chemie (International ed. in English)》2011,50(36):8316-8319
Let's get radical: A general synthetic route toward angularly ortho-fused polyaromatic [4]helicenes starting from aryl alkenyl N-substituted cyclic enediynes is described (see scheme; DMSO=dimethyl sulfoxide, Ns=4-nitrobenzenesulfonyl). The process involved a Bergman cyclization (BC) as the key step of an unprecedented tandem radical reaction. 相似文献
139.
An acyclic amino-receptor based bi-fluorophoric signaling system 3 exhibits water-induced simultaneous dual channel chromogenic and fluorogenic signal modulation. Its micromolar solution in various organic solvents exhibits an enhancement in absorption in the presence of water in trace amounts through the water-induced delactonization of rhodamine dye, rendering a visual perception as a function of colour change. The presence of water molecules also facilitates a fluorescence resonance energy transfer (FRET) from the excited nitro-benz-oxa-diazole fluorophore to rhodamine dye of 3 and leads to an enhancement of emission up to a second order of magnitude. The failure of the reference compounds 2 and 4 to respond under similar conditions reveals the role of structural variation of the receptor on the perturbation of photophysical processes. 相似文献
140.
Liu G Yasumitsu T Zhao L Peng X Wang F Bauri AK Aonuma S Kimura T Komatsu N 《Organic & biomolecular chemistry》2012,10(30):5830-5836
Handedness- and diameter-based separation of single-walled carbon nanotubes was achieved through preferential extraction of 76-CoMoCAT with 2,6-pyridylene-bridged chiral diporphyrin nanotweezers. 相似文献