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Catalytically Active (catalytically + active)
Terms modified by Catalytically Active Selected AbstractsNew Generation of Gold Catalysts: Nanoporous Foams and Tubes,Is Unsupported Gold Catalytically Active?CHEMPHYSCHEM, Issue 13 2007Masatake Haruta Prof. Dr. Gold fever: Gold turns out to be catalytically very active, provided that either one or two of the three conditions shown in the graphic are fulfilled. In CO oxidation at room temperature even unsupported gold is active in the presence of alkaline water. The active states of gold in the gold catalysts reported so far can be classified into four groups: bulk gold, nanoparticles, clusters or thin layers with specific sizes, and cations. [source] Generation of catalytically active 6-phosphofructokinase from Saccharomyces cerevisiae in a cell-free systemFEBS JOURNAL, Issue 15 2000Anke Edelmann PFK1 and PFK2 coding for the subunits of 6-phosphofructokinase from Saccharomyces cerevisiae were cloned into plasmids suitable for runoff transcription. In vitro translation products of both kinds of subunit were obtained using rabbit reticulocyte lysate as the synthesis and folding system. They were monitored by chemiluminescent Western-blot analysis. Folding and assembly of the ,-subunit and ,-subunit of 6-phosphofructokinase were found to occur in the cell-free system resulting in an enzymatically active protein. The in vitro generated enzyme exhibits a folding state that is similar to that of the heterooctameric form of 6-phosphofructokinase in the presence of fructose 6-phosphate, ATP and ammonium sulfate, as demonstrated by size-exclusion HPLC followed by ELISA. [source] Protein Nanoparticle Templates: Constrained Synthesis and Organization of Catalytically Active Metal Nanoparticles by Self-Assembled Protein Templates (Adv. Mater.ADVANCED MATERIALS, Issue 34 200934/2009) Novel geometrical architectures of hybrid nanoparticle/protein complexes can be generated by chemically synthesizing monodisperse metal nanoparticles in situ in the presence of a stable, stress-related protein, report Silke Behrens, Oded Shoseyov, and co-workers on p. 3515. The particles are catalytically active and can reduce 4-nitrophenol, and are potentially useful as future biofunctional nanoparticle labels for catalytic signal amplification in optical assays. [source] Arylethyne Bromoboration,Negishi Coupling Route to E - or Z -Aryl-Substituted Trisubstituted Alkenes of ,98% Isomeric Purity.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2010New Horizon in the Highly Selective Synthesis of Trisubstituted Alkenes Abstract The hitherto unprecedented palladium-catalyzed cross-coupling of (Z)-,-bromo-,-arylethenylboranes can be made to proceed satisfactorily through (1) the use of highly catalytically active bis(tri- tert -butylphosphine)palladium or dichloro[N,N -bis-(2,6-diisopropylphenyl)imidazol-2-yl](m -chloropyridine)palladium and (2) conversion of the dibromoboryl group to the (pinacol)boryl group. Thus, a wide variety of carbon groups can be used to substitute bromine in ,98% stereo- and regioselectivity, while suppressing the otherwise dominant ,-debromoboration. Together with the alkylethyne-based protocols, the alkyne bromoboration,Negishi coupling tandem process has emerged as the most widely applicable and highly selective route to trisubstituted alkenes including those that are otherwise difficult to access. [source] Cooperative Catalysis in the Hydrolytic Kinetic Resolution of Epoxides by Chiral [(salen)Co(III)] Complexes Immobilized on Gold ColloidsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2008Thomas Belser Abstract Chiral salen ligands were incorporated into self-assembled thiolate monolayers (SAMs) on gold colloids. Treatment of the immobilized ligand with Co(OAc)2,4,H2O yielded the corresponding [(salen)Co(II)] complex, and aerobic oxidation in the presence of triflic acid afforded the catalytically active [(salen)Co(III)] complex. Functionalized gold colloids with a diameter of 3.4,nm, coated with a mixed monolayer of n -octanethiolates and thiolates with chiral [(salen)Co(III)] end groups were studied as catalysts in the hydrolytic kinetic resolution (HKR) of hexene-1-oxide. Extremely high selectivitiy and significant rate acceleration relative to homogeneous monomeric catalysts were observed. Recovery of the immobilized catalyst was accomplished by simple filtration, and catalyst reoxidation and repeated recycling (seven times) was possible with no loss of reactivity or enantioselectivity. [source] Memory Effects in Palladium-Catalyzed Allylic Alkylations of 2-Cyclohexen-1-yl AcetateADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17-18 2007Nina Svensen Abstract The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employed were (,3 -allyl)PdLCl, where L is a monophosphine ligand [PPh3, PCy3, P(2-BiPh)Cy2, or P(t- Bu)3], all of which afforded enantiospecificity to some extent (5,47,%). Quantum mechanical calculations show that, theoretically, the enantiospecificity should be high due to a preference for the "trans to P" transition state in both formation of the ,3 -allyl intermediate and nucleophilic attack. However, the observed enantiospecificity is relatively low due to isomerization of the ,3 -allyl intermediate and/or dynamic equilibria between the catalytically active (,3 -allyl)PdLCl species and [(,3 -allyl)PdL2]+ or [(,3 -allyl)PdCl]2. It was also observed experimentally that increasing the bulk of the phosphine inhibits formation of the [(,3 -allyl)PdL2]+ complexes, significantly increasing the observed enantiospecificity for some of the ligands. [source] Cloning, sequencing, heterologous expression, and characterization of murine cytochrome P450 3a25*(Cyp3a25), a testosterone 6,-hydroxylaseJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2001Ding Dai Abstract A full-length cDNA clone encoding a novel form of the cytochrome P450 3A subfamily (Cyp3a-25) has been isolated from a mouse liver cDNA library. The sequence contained 2010 base pairs and encoded a protein with 503 amino acids. The amino acid sequence shared greater identities with rat CYP3A18 (90%) and golden hamster CYP3A10 (81%) sequences than with known mouse sequences (Cyp3a-11, Cyp3a-13, Cyp3a-16, and Cyp3a-41 [68,70%]). CYP3A25 was expressed in the Escherichia coli PCWori+ expression vector following slight modifications of the N- and C-terminals of the cDNA. The purified CYP3A25 was recognized on an immunoblot by CYP3A1 antibody and has a molecular weight of 50 kD. CYP3A25 was catalytically active in the 6,-hydroxylation of testosterone and the N-demethylation of benzphetamine and erythromycin. It was demonstrated by RT-PCR that the CYP3A25 mRNA is present in both fetal and adult tissues, including liver, lung, intestines, kidney, and brain. Northern blotting demonstrated that expression is greatest in the liver and small intestine. © 2001 John Wiley & Sons, Inc. J Biochem Mol Toxicol 15:90,99, 2001 [source] Affinity and catalytic heterogeneity of polyclonal myelin basic protein-hydrolyzing IgGs from sera of patients with multiple sclerosisJOURNAL OF CELLULAR AND MOLECULAR MEDICINE, Issue 3 2010Galina A. Legostaeva Abstract Human myelin basic protein (hMBP)-hydrolyzing activity was recently shown to be an intrinsic property of antibodies (Abs) from multiple sclerosis (MS) patients. Here, we present the first evidence demonstrating a significant diversity of different fractions of polyclonal IgGs (pIgGs) from MS patients in their affinity for hMBP and in the ability of pIgGs to hydrolyze hBMP at different optimal pHs (3,10.5). IgGs containing ,- and ,-types of light chains demonstrated comparable relative activities in the hydrolysis of hMBP. IgGs of IgG1,IgG4 sub-classes were analyzed for catalytic activity. IgGs of all four sub-classes were catalytically active, with their contribution to the total activity of Abzs in the hydrolysis of hMBP and its 19-mer oligopeptide increasing in the order: IgG1 (1.5,2.1%) < IgG2 (4.9,12.8%) < IgG3 (14.7,25.0%) < IgG4 (71,78%). Our findings suggest that the immune systems of individual MS patients generate a variety of anti-hMBP abzymes with different catalytic properties, which can attack hMBP of myelin-proteolipid shell of axons, playing an important role in MS pathogenesis. [source] Zinc regulates the ability of Cdc25C to activate MPF/cdk1JOURNAL OF CELLULAR PHYSIOLOGY, Issue 1 2007Lu Sun Zn2+ is an essential micronutrient for the growth and development of multicellular organisms, as Zn2+ deficiencies lead to growth retardation and congenital malformations (Vallee, BL, Falchuk, KH. 1993. Physiol Rev., 73:79,118). At the cellular level Zn2+ depravation results in proliferation defects in many cell types (Vallee, BL, Falchuk, KH. 1993. Physiol Rev., 73:79,118), however the molecular pathways involved remain poorly defined. Here we show that the transition metal chelator TPEN (N,N,N,,N,-tetrakis(2-pyridylmethyl) ethylene diamine) blocks the G2/M transition of the meiotic cell cycle by inhibiting Cdc25C-cdk1 activation. ICP-MS analyses reveal that Cdc25C is a Zn2+ -binding metalloprotein, and that TPEN effectively strips Zn2+ away from the enzyme. Interestingly, although apo-Cdc25C (Zn2+ -deficient) remains fully catalytically active, it is compromised in its ability to dephosphorylate and activate MPF/cdk1. Thus, Zn2+ is an important regulator of Cdc25C function in vivo. Because of the conserved essential role of the Cdc25C-cdk1 module in the eukaryotic cell cycle, these studies provide fundamental insights into cell cycle regulation. J. Cell. Physiol. 213: 98,104, 2007. © 2007 Wiley-Liss, Inc. [source] Developing bifunctional , -lactamase molecules with built-in target-recognizing module for prodrug therapy: identification of Enterobacter Cloacae P99 cephalosporinase loops suitable for randomization and phage-display selectionJOURNAL OF MOLECULAR RECOGNITION, Issue 6 2009Girja S. Shukla Abstract This study was focused on developing catalytically active , -lactamase enzyme molecules that have target-recognizing sites built within their scaffold. Using phage-display approach, nine libraries were constructed by inserting the randomized linear or cysteine-constrained heptapeptides in the five different loops on the outer surface of P99 , -lactamase molecule. The pIII signal peptide of Sec-pathway was employed for a periplasmic translocation of the , -lactamase fusion protein, which we found more efficient than the DsbA signal peptide of SRP-pathway. The randomized heptapeptide loops replaced native amino acids between positions 34Y- 37K, 238M- 246A, 275N- 280A, 305A- 311S, or 329I- 334I of the P99 , -lactamase molecules for generating the loop-1 to -5 libraries, respectively. The diversity of each loop library was judged by counting the primary and , -lactamase-active clones. The linear peptide inserts in the loop-2 library showed the maximum number of the , -lactamase-active clones, followed by the loop-5, loop-3, and loop-4. The insertion of the cysteine-constrained loops exhibited a dramatic loss of the enzyme-active , -lactamase clones. The complexity of the loop-2 linear library, as determined by the frequency and diversity of amino acid distributions in the randomized region, appears consistent with the standards of other types of phage display library systems. The selection of the loop-2 linear library on streptavidin protein as a test target identified several , -lactamase clones that specifically bound to streptavidin. In conclusion, this study identified the suitability of the loop-2 of P99 , -lactamase for constructing a phage-display library of the , -lactamase enzyme-active molecules that can be selected against a target. This is an enabling step in our long-term goal of developing bifunctional , -lactamase molecules against cancer-specific targets for enzyme prodrug therapy of cancer. Copyright © 2009 John Wiley & Sons, Ltd. [source] Expression, purification, and characterization of pro-phenoloxidase-activating serine protease from Spodoptera lituraARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2009Naresh Arora Abstract One of the important trigger molecules for innate immunity is a serine protease that activates zymogen phenol oxidase (PPO). Central to wound healing response is the activation of phenol oxidase zymogen. Molecular characterization of phenol oxidase has been recently reported by us. Here, we report isolation, cloning, expression, and purification of prophenol oxidase activating enzyme 1 (slppae1) from polyphagous pest, Spodoptera litura. SLPPAE1 is induced within 6,h of physical injury. The structural features of the mature polypeptide are reminiscent of other lepidopteran PPAE in having a signal peptide, propeptide, and catalytically active polypeptide. The cDNA has been expressed in Sf21 cells using baculovirus expression vector. Fractionation of expressing Sf21 cells revealed its expression in the membranes. The recombinant protein was solubilized from membranes and purified by Ni-NTA affinity chromatography. The purified enzyme is catalytically active on chromogenic substrate, activates recombinantly expressed prophenol oxidase (PPO) of S. litura, and is sensitive to inhibition by aprotenin. N-terminal sequencing of processed phenol oxidase revealed 11,kDa propeptide instead of in-silico predicted 6,kDa polypeptide. © 2009 Wiley Periodicals, Inc. [source] Structure of the Methanothermobacter thermautotrophicus exosome RNase PH ringACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2010C. Leong Ng The core of the exosome, a versatile multisubunit RNA-processing enzyme found in archaea and eukaryotes, includes a ring of six RNase PH subunits. This basic architecture is homologous to those of the bacterial and archaeal RNase PHs and the bacterial polynucleotide phosphorylase (PNPase). While all six RNase PH monomers are catalytically active in the homohexameric RNase PH, only half of them are functional in the bacterial PNPase and in the archaeal exosome core and none are functional in the yeast and human exosome cores. Here, the crystal structure of the RNase PH ring from the exosome of the anaerobic methanogenic archaeon Methanothermobacter thermautotrophicus is described at 2.65,Å resolution. Free phosphate anions were found for the first time in the active sites of the RNase PH subunits of an exosome structure and provide structural snapshots of a critical intermediate in the phosphorolytic degradation of RNA by the exosome. Furthermore, the present structure highlights the plasticity of the surfaces delineating the polar regions of the RNase PH ring of the exosome, a feature that can facilitate both interaction with the many cofactors involved in exosome function and the processive activity of this enzyme. [source] DNA methylation with a sting: An active DNA methylation system in the honeybeeBIOESSAYS, Issue 3 2007Matthias Schaefer The existence of DNA methylation in insects has been a controversial subject over a long period of time. The recently completed genome sequence of the honeybee Apis mellifera has revealed the first insect with a full complement of DNA methyltransferases.1 A parallel study demonstrated that these enzymes are catalytically active and that Apis genes can be methylated in specific patterns.2 These findings establish bees as a model to analyze the function of DNA methylation systems in invertebrate organisms and might also be important to understand evolutionary aspects of DNA methylation in higher eukaryotes. BioEssays 29: 208,211, 2007. © 2007 Wiley Periodicals, Inc. [source] The Catalytic Acylcyanation of IminesCHEMISTRY - AN ASIAN JOURNAL, Issue 2 2008Chandra Pan, Subhas Abstract The catalytic acylcyanation of aldimines with acylcyanides and a direct three-component variant involving the generation of an imine in,situ have been developed. Furthermore, a highly enantioselective version has been established, culminating in the first organocatalytic asymmetric three-component Strecker reaction. Jacobsen thiourea catalysts were found to catalyze the reaction with excellent enantioselectivities, whereas binol phosphates (binol=1,1,-bi-2,2,-naphthol) proved to be catalytically active but only modestly enantioselective. A large number of different substrates could be used in the processes described, thus illustrating the potential of our reaction for the generation of diversity within the attractive ,-amino carbonyl framework. Furthermore, a novel cyclic amidine was obtained from the reaction of acetyl cyanide with ketimines. Die katalytische Acylcyanierung von Iminen mit Acetylcyanid und ihre direkte Dreikomponentenvariante wurden entwickelt. Darüber hinaus konnte eine hoch-enantioselelektive Version beschrieben werden, die schließlich zur Entdeckung der ersten organokatalytischen asymmetrischen Dreikomponenten-Strecker-Reaktion führte. Jacobsens Thioharnstoff-Katalysatoren katalysieren die Reaktion mit hohen Enantioselektivitäten während Binol-Phosphorsäuren die Reaktion zwar katalysieren, aber dabei nur mäßige Enantioselektivitäten liefern. Eine Reihe verschiedener Substrate konnten in den beschriebenen Verfahren eingesetzt werden, wobei das Potential der Reaktion für die Erzeugung von Diversität innerhalb der attraktiven ,-Aminocarbonyl Substratklasse illustriert wurde. Darüber hinaus wurde eine neue Klasse zyklische Amidine in der Reaktion von Acetylcyanid mit Ketiminen erzeugt. [source] | |||||||||||||