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排序方式: 共有140条查询结果,搜索用时 15 毫秒
101.
Landon P Collier PJ Papworth AJ Kiely CJ Hutchings GJ 《Chemical communications (Cambridge, England)》2002,(18):2058-2059
Supported Au catalysts are very selective for the direct formation of hydrogen peroxide from H2/O2 mixtures at 2 degrees C; the rate of H2O2 synthesis is markedly increased if Au-Pd alloy nanoparticles are generated by the addition of Pd. 相似文献
102.
Collier P Golunski S Malde C Breen J Burch R 《Journal of the American Chemical Society》2003,125(41):12414-12415
A coherent layer of zeolite A has been applied to a SiO2-supported Pt-Fe oxidation catalyst, using total surface charge-reversal. The zeolite has tracked the metals into the pore structure of the support, covering the active sites. The zeolite channel size is large enough to allow access of CO and O2 to the active sites, and to allow CO2 to emerge, but it excludes larger molecules. The presence of the zeolite membrane transforms the supported Pt-Fe into a highly specific catalyst, which can discriminate between CO and butane, even after the macroscopic catalyst particles are crushed. 相似文献
103.
104.
Synthesis of Vibegron Enabled by a Ketoreductase Rationally Designed for High pH Dynamic Kinetic Reduction
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Dr. Feng Xu Dr. Birgit Kosjek Dr. Fabien L. Cabirol Dr. Haibin Chen Richard Desmond Dr. Jeonghan Park Anupam P. Gohel Dr. Steven J. Collier Dr. Derek J. Smith Dr. Zhuqing Liu Dr. Jacob M. Janey Dr. John Y. L. Chung Dr. Oscar Alvizo 《Angewandte Chemie (International ed. in English)》2018,57(23):6863-6867
Described here is an efficient stereoselective synthesis of vibegron enabled by an enzymatic dynamic kinetic reduction that proceeds in a high‐pH environment. To overcome enzyme performance limitations under these conditions, a ketoreductase was evolved by a computationally and structurally aided strategy to increase cofactor stability through tighter binding. 相似文献
105.
T. D. Klots P. Devlin W. B. Collier 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》1997,53(14)
Infrared and Raman measurements for benzimidazole are presented and discussed, including its argon-matrix infrared spectrum. To assist in the assignment, benzimidazole's harmonic force fields for the 321G* and 631G* levels were scaled by scaled factors derived by fitting the respective computed force fields of other indene derivatives to previously reported experimental vibrational frequencies. Comparison to the best set of experimental wavenumbers, usually taken from the matrix, shows mean 321G* and 631G* deviations of 7.0 and 5.8 cm−1 for the planar modes, and 14.0 and 6.8 cm−1 for the nonplanar modes, respectively, with much of the error residing in imino-hydrogen group modes. Standard entropies are derived with the matrix wavenumbers and the methods of statistical mechanics. An attempt to determine standard entropies by calorimetric methods was unsuccessful. The triple-point temperature Ttp and enthalpy of fusion Δ1crHm only are reported. 相似文献
106.
Structure-activity relationships in purine-based inhibitor binding to HSP90 isoforms. 总被引:3,自引:0,他引:3
Lisa Wright Xavier Barril Brian Dymock Louisa Sheridan Allan Surgenor Mandy Beswick Martin Drysdale Adam Collier Andy Massey Nick Davies Alex Fink Christophe Fromont Wynne Aherne Kathy Boxall Swee Sharp Paul Workman Roderick E Hubbard 《Chemistry & biology》2004,11(6):775-785
Inhibition of the ATPase activity of the chaperone protein HSP90 is a potential strategy for treatment of cancers. We have determined structures of the HSP90alpha N-terminal domain complexed with the purine-based inhibitor, PU3, and analogs with enhanced potency both in enzyme and cell-based assays. The compounds induce upregulation of HSP70 and downregulation of the known HSP90 client proteins Raf-1, CDK4, and ErbB2, confirming that the molecules inhibit cell growth by a mechanism dependent on HSP90 inhibition. We have also determined the first structure of the N-terminal domain of HSP90beta, complexed with PU3. The structures allow a detailed rationale to be developed for the observed affinity of the PU3 class of compounds for HSP90 and also provide a structural framework for design of compounds with improved binding affinity and drug-like properties. 相似文献
107.
Avril Collier Joseph Wang Dermot Diamond Eithne Dempsey 《Analytica chimica acta》2005,550(1-2):107-115
A miniaturised analytical system for separating and detecting a range of steroidal oestrogens, based on the coupling of a micromachined capillary electrophoresis chip with glassy-carbon electrode amperometric detector, is described. Factors influencing the on-chip separation utilising the technique micellar electrokinetic chromatography (MEKC) and detection processes are optimised. The addition of modifiers such as organic solvents and surfactants improve separation and resolution of these hydrophobic compounds. Using a borate running buffer (5 mM, pH 11) with 20% methanol and SDS (20 mM) and a separation voltage of 2000 V, baseline resolution is observed for 16-keto-17β-oestradiol, oestriol, 11β-hydroxyoestradiol, oestrone, and β-oestradiol in 420 s with limits of detection 16–84 μM. The implications for on-site environmental analysis are discussed. 相似文献
108.
R. P. Bhalerao J. L. Collier P. Gustafsson A. R. Grossman 《Photochemistry and photobiology》1995,61(3):298-302
Abstract— The effect of elimination of the 30, 33 and 9 kDa phycobilisome rod-linker polypeptides on rod length was examined by electron microscopy of phycobilisomes isolated from wild-type Synechococcus sp. strain PCC 7942 and from genetically engineered mutants with lesions in the genes encoding the rod-linker polypeptides. The maximum rod length in the absence of the 33 kDa linker polypeptide was two phycocyanin hexamers, whereas rods with up to five hexamers were found in the mutant strain lacking the 30 kDa linker polypeptide. Elimination of the 9 kDa linker polypeptide did not have a significant effect on rod length. Finally, mutants lacking either the 30 or 33 kDa rod-associated linker polypeptides had an increased number of rods that terminated with a phycocyanin trimer. These observations are discussed with respect to the role of the linker polypeptides in the biosynthesis of the rod substructure. 相似文献
109.
L. Láska J. Krása K. Mašek M. Pfeifer B. Králiková T. Mocek J. Skála P. Straka P. Trenda K. Rohlena E. Woryna J. Farny P. Parys J. Wołowski W. Mróz A. Shumshurov B. Sharkov J. Collier K. Langbein H. Haseroth 《Czechoslovak Journal of Physics》1996,46(11):1099-1115
The results of systematic studies of multiply charged Ta ion production with the fundamental frequency of an iodine laser (=1.315m), and its 2nd (0.657m) and 3rd (0.438m) harmonics are summarized and discussed. Short laser pulse (350 ps) and a focus spot diameter of 100m allowed for the laser power densities in the range of 5×1013–1.5×1015 W/cm2. Corpuscular diagnostics were based on time-of-flight methods; two types of ion collectors and a cylindrical electrostatic ion energy analyzer were used. The Ta ions with charge state up to 55+ were registered in the distance of 210 cm; the maximum amplitude of the signal of a high energy ion group was found to belong to the ions with the charge state around 43+, depending on the laser power density. The ion energy distribution was measured for all three wavelengths, however, in a different energy range; the maximum registered ion energy was 8.8 MeV. The occurrence of highly charged ions in the far expansion zone is discussed in view of the mechanism of charge distribution freezing during two-temperature isothermal plasma expansion.The work was performed in a partial fulfillment of the research grant project No. A1010525 sponsored by the Academy of Sciences of the Czech Republic and grant project No. 202/95/0039 sponsored by the Grant Agency of the Czech Republic. 相似文献
110.
Kember GC Fenton GA Collier K Armour JA 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》2000,61(2):1816-1824
Aperiodic stochastic resonance (ASR) is studied for a densely interconnected population of excitatory and inhibitory neurons that exhibit hysteresis. Switching between states in the presence of noisy external forcing is represented as a "competition between averages" and this is further explained through a semianalytical model. In contrast to energy-based approaches where only the timing of a switch between states is represented, the competition between averages also identifies the input history responsible for a switch. This last point leads to some interesting conclusions regarding cause and effect in the presence of noisy forcing of a hysteretic system. For example, at subthreshold inputs, it is found that the input history causing a switch between states is primarily dependent upon the noise level even though the corresponding time to switch is sensitive to both the distance from the threshold and the noise level. Since the application considered here is to cardiac neuronal control, control performance is considered over the full input range. Noise tuning for adequate control performance is found to be unnecessary if the noise level is high enough. This is consistent with studies of ASR for sensory neurons. Another observation made here that may be of clinical significance is that at higher noise levels, constraints placed upon inputs to ensure adequate control performance are likely to depend upon the switching direction. 相似文献