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Inhibition Reaction (inhibition + reaction)
Selected AbstractsElectrochemical Characteristics of Mediated Laccase-Catalysis and Electrochemical Detection of Environmental PollutantsELECTROANALYSIS, Issue 8 2008Ying Liu Abstract Laccase has been immobilized on the carbon nanotubes modified glassy carbon electrode surface by adsorption. As-prepared laccase retains good electrocatalytic activity to oxygen reduction by using 2,2,-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) as the mediator. It can be used as a biosensor for the determination of catechol with broad linear range. Especially, azide, one of inhibitors of laccase, shows sensitive inhibition to catalytic activity of the laccase modified electrode. In addition, the inhibition by fluoride ions has also been studied. These demonstrate that the as-prepared electrode can be used to detect halide and some the toxic pollutants, e.g., catechol and azide based on catalytic or inhibition reaction of laccase. The simple preparation procedure makes the system can be developed as non-inhibition or inhibition biosensor. [source] 2,4-Dioxa-7-aza-, 2,4-Dioxa-8-aza-, and 2,4-Dioxa-9-aza-3-phosphadecalins as Rigid Acetylcholine Mimetics: Syntheses and CharacterizationHELVETICA CHIMICA ACTA, Issue 10 2004Stefan Furegati Phosphorylation of suitable piperidine precursors yielded a series of novel decalin-type O,N,P-heterocycles. The title compounds, P(3)-axially and P(3)-equatorially X-substituted, cis- and trans- configurated 2,4-dioxa-7-aza-, 2,4-dioxa-8-aza-, and 2,4-dioxa-9-aza-3-phosphabicyclo[4.4.0]decane 3-oxides (X=Cl, F, 4-nitrophenoxy, and 2,4-dinitrophenoxy), are configuratively fixed and conformationally constrained P-analogues of acetylcholine and as such represent acetylcholine (7-aza and 9-aza isomers) or , -homo-acetylcholine mimetics (8-aza isomers). Being irreversible inhibitors of acetylcholinesterase (AChE), the compounds are considered to be suitable probes for the investigation of the stereochemical course of the inhibition reaction by 31P-NMR spectroscopy. Moreover, the design of these mimetics will enable studies of molecular interactions with AChE, in particular, the recognition conformation of acetylcholine. [source] Characterization of covalently inhibited extracellular lipase from Streptomyces rimosus by matrix-assisted laser desorption/ionization time-of-flight and matrix-assisted laser desorption/ionization quadrupole ion trap reflectron time-of-flight mass spectrometry: localization of the active site serine,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2004Martin Zehl Abstract A chemical modification approach combined with matrix-assisted laser desorption/ionization (MALDI) mass spectrometry was used to identify the active site serine residue of an extracellular lipase from Streptomyces rimosus R6-554W. The lipase, purified from a high-level overexpressing strain, was covalently modified by incubation with 3,4-dichloroisocoumarin, a general mechanism-based serine protease inhibitor. MALDI time-of-flight (TOF) mass spectrometry was used to probe the nature of the intact inhibitor-modified lipase and to clarify the mechanism of lipase inhibition by 3,4-dichloroisocoumarin. The stoichiometry of the inhibition reaction revealed that specifically one molecule of inhibitor was bound to the lipase. The MALDI matrix 2,6-dihydroxyacetophenone facilitated the formation of highly abundant [M + 2H]2+ ions with good resolution compared to other matrices in a linear TOF instrument. This allowed the detection of two different inhibitor-modified lipase species. Exact localization of the modified amino acid residue was accomplished by tryptic digestion followed by low-energy collision-induced dissociation peptide sequencing of the detected 2-(carboxychloromethyl)benzoylated peptide by means of a MALDI quadrupole ion trap reflectron TOF instrument. The high sequence coverage obtained by this approach allowed the confirmation of the site specificity of the inhibition reaction and the unambiguous identification of the serine at position 10 as the nucleophilic amino acid residue in the active site of the enzyme. This result is in agreement with the previously obtained data from multiple sequence alignment of S. rimosus lipase with different esterases, which indicated that this enzyme exhibits a characteristic Gly-Asp-Ser-(Leu) motif located close to the N-terminus and is harboring the catalytically active serine residue. Therefore, this study experimentally proves the classification of the S. rimosus lipase as GDS(L) lipolytic enzyme. Copyright © 2004 John Wiley & Sons, Ltd. [source] Kinetic and mechanistic studies on the inhibition of free radical-initiated polymerization of styrene by ,-carotene and ,-tocopherolJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 6 2002Zhaolong Li Abstract The inhibition of free radical-initiated polymerization of styrene by ,-carotene (,C) and ,-tocopherol (TOH) was studied by dilatometry. The polymerization was initiated by 2,2,-azobis(isobutyronitrile) at 50,°C in chlorobenzene and inhibited by ,C and/or TOH. It was found that ,C and TOH could efficiently inhibit the polymerization, either used individually or in combination, and a significant synergistic effect was observed when they were used in combination. It is proposed that retinal, which is the principal oxidation product of ,C, may be involved in the synergistic inhibition reaction of ,C and TOH. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||