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Catalytic Ability (catalytic + ability)
Selected AbstractsA B3LYP Study for the Adsorption and Catalytic Ability of BF3 on NiO(001) Surface.CHEMINFORM, Issue 5 2006Wenfeng Wang No abstract is available for this article. [source] Contrast Performance in Catalytic Ability , New Cinchona Phase Transfer Catalysts for Asymmetric Synthesis of ,-Amino Acids.CHEMINFORM, Issue 23 2005Shanmugam Elango Abstract For Abstract see ChemInform Abstract in Full Text. [source] Hexahydropyrrolo[2,3- b]indoles: A New Class of Structurally Rigid Tricyclic Skeleton for Oxazaborolidine-Catalyzed Asymmetric Borane ReductionADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7 2010Jian Xiao Abstract A new class of structurally rigid tricyclic chiral ligands based on the hexahydropyrrolo[2,3- b]indole skeleton has been rationally designed and the catalytic abilities in asymmetric catalysis have been shown in the enantioselective borane reduction of prochiral ketones to afford the chiral alcohols in excellent yields and high enantioselectivities (up to 97% ee). [source] Electroactivity of Polyaniline Multilayer Films in Neutral Solution and Their Electrocatalyzed Oxidation of ,-Nicotinamide Adenine DinucleotideADVANCED FUNCTIONAL MATERIALS, Issue 6 2003S. Tian Abstract In this paper, we report an alternative simple method to shift the electroactivity of polyaniline (PANI) films to neutral pH conditions by forming multilayer assemblies with poly(anions) using the layer-by-layer (LBL) deposition method. A series of self-assembled PANI multilayer films with poly(anions), such as sulfonated polyaniline (SPANI), poly(acrylic acid) (PAA), poly(vinyl sulfonate) (PVS), and poly(styrene sulfonate) (PSS), were prepared by the LBL method. Their electrochemical behavior and catalytic ability for the oxidation of ,-nicotinamide adenine dinucleotide (NADH) in neutral solution were investigated by electrochemistry (EC) combined with surface plasmon spectroscopy (SPS) and the quartz crystal microbalance (QCM) technique. Results indicated that all the films showed very good stability, reversibility, and electroactivity in neutral solution. All the multilayer films can electrocatalyze the oxidation of NADH, with the catalytic ability of PANI/SPANI being higher than that of the other assemblies under the same conditions. The catalytic abilities of the films with the same thickness prepared by the copolymerization method and the LBL method were also compared. [source] Metal-Free: An Efficient and Selective Catalytic Aerobic Oxidation of Hydrocarbons with Oxime and N -HydroxyphthalimideADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Gengxiu Zheng Abstract A non-metal catalytic system consisting of dimethylglyoxime (DMG) and N -hydroxyphthalimide (NHPI) for the selective oxidation of hydrocarbons with dioxygen is described. The synergistic effect of DMG and NHPI ensures its efficient catalytic ability: 82.1% conversion of ethylbenzene with 94.9% selectivity for acetophenone could be obtained at 80,°C under 0.3,MPa of dioxygen in 10,h. Several hydrocarbons were efficiently oxidized to their corresponding oxygenated products under mild conditions. [source] Chain-length specificities of maize starch synthase I enzyme: studies of glucan affinity and catalytic propertiesTHE PLANT JOURNAL, Issue 5 2001Padmavathi D. Commuri Summary It is widely known that some of the starch synthases and starch-branching enzymes are trapped inside the starch granule matrix during the course of starch deposition in amyloplasts. The objective of this study was to use maize SSI to further our understanding of the protein domains involved in starch granule entrapment and identify the chain-length specificities of the enzyme. Using affinity gel electrophoresis, we measured the dissociation constants of maize SSI and its truncated forms using various glucans. The enzyme has a high degree of specificity in terms of its substrate,enzyme dissociation constant, but has a greatly elevated affinity for increasing chain lengths of ,-1, 4 glucans. Deletion of the N-terminal arm of SSI did not affect the Kd value. Further small deletions of either N- or C-terminal domains resulted in a complete loss of any measurable affinity for its substrate, suggesting that the starch-affinity domain of SSI is not discrete from the catalytic domain. Greater affinity was displayed for the amylopectin fraction of starch as compared to amylose, whereas glycogen revealed the lowest affinity. However, when the outer chain lengths (OCL) of glycogen were extended using the phosphorylase enzyme, we found an increase in affinity for SSI between an average OCL of 7 and 14, and then an apparently exponential increase to an average OCL of 21. On the other hand, the catalytic ability of SSI was reduced several-fold using these glucans with extended chain lengths as substrates, and most of the label from [14C]ADPG was incorporated into shorter chains of dp < 10. We conclude that the rate of catalysis of SSI enzyme decreases with the OCL of its glucan substrate, and it has a very high affinity for the longer glucan chains of dp ,20, rendering the enzyme catalytically incapable at longer chain lengths. Based on the observations in this study, we propose that during amylopectin synthesis shorter A and B1 chains are extended by SSI up to a critical chain length that soon becomes unsuitable for catalysis by SSI and hence cannot be elongated further by this enzyme. Instead, SSI is likely to become entrapped as a relatively inactive protein within the starch granule. Further glucan extension for continuation of amylopectin synthesis must require a handover to other SS enzymes which can extend the glucan chains further or for branching by branching enzymes. If this is correct, this proposal provides a biochemical basis to explain how the specificities of various SS enzymes determine and set the limitations on the length of A, B, C chains in the starch granule. [source] Regulation of ,-Chymotrypsin Catalysis by Ferric Porphyrins and CyclodextrinsCHEMISTRY - AN ASIAN JOURNAL, Issue 4 2008Koji Kano Prof. Abstract Positively charged ,-chymotrypsin (ChT) formed a 1:1 complex with negatively charged 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron(III) (FeTPPS) in phosphate buffer at pH,7.4 through electrostatic interaction. In spite of the large binding constant (K=4.8×105,M,1), FeTPPS could not completely inhibit the catalysis of ChT in the hydrolysis of the model substrate, N -succinyl- L -phenylalanine p -nitroanilide (SPNA). The degree of inhibition (60,%) was saturated at 1.6,equivalents of FeTPPS, which indicates that covering of the active site of ChT by FeTPPS was insufficient. The enzymatic activity lowered by FeTPPS was entirely recovered for the freshly prepared sample when the porphyrin on the protein surface was detached by per- O -methylated ,-cyclodextrin (TMe-,-CD), which formed a stable 1:2 inclusion complex with FeTPPS (K1=1.26×106,M,1, K2=6.3×104,M,1). FeTPPS gradually induced irreversible denaturation of ChT, and the denatured ChT further lost its catalytic ability. No repairing effect of TMe-,-CD was observed with irreversibly denatured ChT. A new reversible inhibitor, 5,10,15,20-tetrakis[4-(3,5-dicarboxyphenylmethoxy)phenyl]porphyrinato iron(III) (FeP8M), was then designed, and its inhibitory behavior was examined. FeP8M formed very stable 1:1 and 1:2 FeP8M/ChT complexes with ChT, the K1 and K2 values being 2.0×108 and 1.0×106,M,1, respectively. FeP8M effectively inhibited the ChT-catalyzed hydrolysis of SPNA (maximum degree of inhibition=85,%), and the activity of ChT was recovered by per- O -methylated ,-cyclodextrin. No irreversible denaturation of ChT occurred upon binding with FeP8M. The kinetic data support the observation that, for nonincubated samples, both inhibitors did not cause significant conformational change in ChT and inhibited the ChT activity by covering the active site of the enzyme. [source] Low-Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow SpheresCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2007Huifang Xu Abstract This report presents a facile approach for the low-temperature synthesis of crystalline inorganic-oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic-oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in,situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high- , -gate dielectrics, and photocatalysis. [source] | ||||||||||