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81.
82.
83.
Chapman E Ding S Schultz PG Wong CH 《Journal of the American Chemical Society》2002,124(49):14524-14525
In the present work, we have used a newly developed, fluorescence-based assay to screen a library of >30 000 compounds as potential beta-arylsulfotransferase-IV inhibitors. A total of 11 inhibitors were discovered. Most of the compounds discovered showed low micromolar inhibition, but one of the compounds showed potent inhibition (Ki = 96 nM). The most potent of these inhibitors was tested against a variety of other purine binding enzymes and showed remarkable specificity. 相似文献
84.
Wong EL Chow E Gooding JJ 《Langmuir : the ACS journal of surfaces and colloids》2005,21(15):6957-6965
The effect of the surface chemistry of DNA recognition interfaces on DNA hybridization at a gold surface was investigated using both electrochemistry and the quartz crystal microbalance (QCM) technique. Different DNA recognition interfaces were prepared using a two-component self-assembled monolayer consisting of thiolated 20-mer probe single-stranded DNA (ss-DNA) containing either a 3'-mercaptopropyl or a 3'-mercaptohexyl linker group and an alcohol-terminated diluent layer with 2-, 6-, or 11-carbon length. The influence of the interfacial design on the hybridization efficiency, the affinity constant (Ka) describing hybridization, and the kinetics of hybridization was assessed. It was found that the further the DNA was above the surface defined by the diluent layer the higher the hybridization efficiency and Ka. The kinetics of DNA hybridization was assessed using both a QCM and an electrochemical approach to ascertain the influence of the interface on both the initial binding of target DNA to the surface and the formation of a complete duplex. These measurements showed that the length of the diluent layer has a large impact on the time taken to form a perfect duplex but no impact on the initial recognition of the target DNA by the immobilized probe DNA. 相似文献
85.
V. E. Noshkin W. L. Robison K. M. Wong R. J. Eagle 《Journal of Radioanalytical and Nuclear Chemistry》1998,234(1-2):243-249
There continue to be reports in the literature that suggest a difference in the behavior of239+240Pu and238Pu in some aquatic environments. Plutonium isotopes have been measured in marine samples collected over 3 decades from Enewetak
atoll, one of the sites in the Marshall Islands used by the United States between 1946 and 1958 to test nuclear devices. The
plutonium isotopes originated from a variety of complex sources and could possibly coexist in this environment as different
physical-chemical species. However results indicate little difference in the mobility and biological availability of239+240Pu and238Pu. 相似文献
86.
Abstract. New results are presented on the effects of mono- and divalent cations on concurrent changes in the microsecond yields and kinetics of chlorophyll a fluorescence and delayed light emission, and the light saturation curve for the latter at 100 μs, following a 10 ns flash at 337 nm. (1) The fluorescence yield increases exponentially from 3 to 30 μs (lifetime, τ, 6.4 ± 0.6/μs), and decays biphasically between 50 and 800μs. (2) The delayed light emission decays biphasically with two exponential phases: fast phase, T= 7–10μs, and slow phase, T= 33–40μs. (3) The light saturation curve for 100μs delayed light emission is satisfactorily represented by a one-hit Poisson saturation curve. (4) Addition of 5 mM NaCl to salt-depleted chloroplasts decreases (by as much as 40%) the yields of μs fluorescence and delayed light emission, and the subsequent addition of 5mM MgCl2 increases the yields (≤2 × over samples with only NaCl). (5) The fluorescence yield rise and delayed light emission decay kinetics are independent of low concentrations of cations. The lifetime of the fast phase of fluorescence decay changes from ?90μs to ?160μs, when Na+ or Na++ Mg2+ are added. Based on a detailed analysis presented in this paper, the following conclusions regarding the effects of low concentrations (few mM) of mono-and divalent cations in sucrose-washed chloroplasts at room temperature are made: (a) Na+ decreases (?6%) and Mg2+ increases (? 20% compared with the Na+ sample) the sensitization of photosystem II photochemistry: this effect is small, but significant. (b) Na+ increases and Mg2+ decreases the efficiency for radiationless transitions in singlet excited Chl a in the antenna and closed reaction center of PS II; this includes non-radiative energy transfer to PS I, intramolecular intersystem crossing and internal conversion. The ratio of the sum of the rate constants for radiationless transitions to that for fluorescence increases by ? 2-fold upon the addition of Na+, and is completely reversed by the addition of Mg2+. (c) The rate constant for the re-oxidation of Q- decreases (about 50%) in the presence of Na+ or Na++ Mg2+. These conclusions imply that cations produce multiple changes in the primary photoprocesses of PS II at physiological temperatures. It is proposed that these changes are mutually independent and can co-exist. 相似文献
87.
A series of new C2-symmetric 2,2′-bipyridine-contaning crown macrocycles 1-4 has been developed for enantiomeric recognition of amino acid derivatives. These new macrocycles have been showed to be strong complexing agents for primary organic ammonium salts (with K up to 4.83×105 M−1 and −ΔG0 up to 32.4 kJ mol−1) and also useful chromophores for UV-vis titration studies. These macrocyclic hosts exhibited enantioselective binding towards the (S)-enantiomer of phenylglycine methyl ester hydrochloride (Am1) with K(S)/K(R) up to 2.10 (ΔΔG0=−1.84 kJ mol−1) in CH2Cl2 with 0.25% CH3OH. The structure-binding relationship studies showed that the aromatic subunit and the ester group of the ammonium guests are both important for good enantioselectivity. In addition, the host-guest complexes have been studied using various NMR experiments. 相似文献
88.
K. P. Sivaramakrishnan C. Samyn Ira John Westerman Daniel Ting-Man Wong C. S. Marvel 《Journal of polymer science. Part A, Polymer chemistry》1975,13(5):1083-1094
1,3-Bis(p-phenoxybenzenesulfonyl)benzene, 4,4′-bis(p-phenoxybenzenesulfonyl)diphenyl ether, and 4,4′-diphenoxydiphenyl sulfone were polymerized with isophthaloyl or terephthaloyl chlorides in Friedel-Crafts type polymerizations. These polymers had [2,2]p-cyclophane units in the backbone, introduced by employing 3,9-bis(p-phenoxybenzoyl) [2.2]p-cyclophane as part of the polyaryl ether component. Thermolysis of the dimethylene bridge of the [2.2]p-cyclophane monomer produced diradicals which combined across polymer chains to provide crosslinks. p-Cyclophane polymers with 1,3-bis-(p-phenoxybenzenesulfonyl)benzene showed potential as high performance, thermally stable laminating resins. 相似文献
89.
Ronald G. Cavell Chih Y. Wong Robert McDonald 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4)
Abstract Neutral hexacoordinate phosphorus(V) compounds of a number of univalent bidentate ligands are known.l,2 The silylated forms of tridentate, dianionic Schiff base ligands: N-(2-hydroxyphenyl)salicylideneamine H2LI, N-(4-tert-butyl-2-hydroxyphenyl)-salicylideneamine H2LII, N-(2-hydroxy-4-nitrophenyl)salicylidene-amine H2LIII, and 2,2′-azodiphenol H2LIV gave, with halogeno- and (trifluoromethyl)halogenophosphoranes, neutral hexa-coordinate derivatives with bis-chelate structures. The ligands form bicyclic five- and six-membered chelate rings in a meridional conformation, with two P-O bonds and one N→P donor bond. Hexacoordinate structures were evidenced by high-field 31P NMR chemical shifts (-136 to -148 ppm), characteristic J PF coupling patterns and was further substantiated by crystal structures of Cl3LII (A) and F3PLII (B). 相似文献
90.
Lai Hong Wong Asier Unciti-Broceta Michaela Spitzer Rachel White Mike Tyers Lea Harrington 《Chemistry & biology》2013,20(3):333-340
Highlights? Growth arrest induced by human telomerase in yeast is chemically reversible ? Readout is sensitive to telomerase catalytic activity and telomere recruitment ? Three cell-permeable compounds also inhibit purified human telomerase ? Yeast can be successfully used to screen for human telomerase inhibitors 相似文献