Topic
Substrate (chemistry)
About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.
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TL;DR: Fluorescence microscopy with a cooled CCD imaging system is used to visualize the spatial distribution of enzyme immobilization sites (indicated by fluorescence from Texas Red-labeled avidin) across the carbon surface and the viability of the enzyme attached to the surface was demonstrated by imaging the distribution of an insoluble, fluorescent product.
Abstract: Micrometer-sized domains of a carbon surface are modified to allow derivatization to attach redox enzymes with biotin/avidin technology. These sites are spatially segregated from and directly adjacent to electron transfer sites on the same electrode surface. The distance between these electron transfer sites and enzyme-loaded domains must be kept to a minimum (e.g., less than 5 μm) to maintain the fast response time and high sensitivity required for the measurement of neurotransmitter dynamics. This is accomplished through the use of photolithographic attachment of photobiotin using an interference pattern from a UV laser generated at the electrode surface. This will allow the construction of microscopic arrays of active enzyme sites on a carbon fiber substrate while leaving other sites underivatized to facilitate electron transfer reactions of redox mediators, thus maximizing enzyme activity and detection of the enzyme mediator. The ultimate sensitivity of these sensors will be realized only through care...
163 citations
TL;DR: Inhibition of the enzyme by carbon monoxide, ionic detergents, sulfhydryl reagents, chelating agents and electron acceptors, together with the demonstrated presence of a b 5 cytochrome and an active NADPH-cytochrome c reductase are discussed as indirect evidence for a microsomal electron transport system in plants similar to those reported for animals.
163 citations
Patent•
09 Jun 2011
TL;DR: In this article, a method for preparing and resulting articles of manufacture comprising a substrate having a surface, a bulk beneath the surface, and a grafted polymer layer on the substrate surface, in combination, constituting a modified surface having a fibrinogen adsorption of less than about 125 ng/cm2.
Abstract: A method for preparing and resulting articles of manufacture comprising a substrate having a surface, a bulk beneath the surface, and a grafted polymer layer on the substrate surface, the substrate surface and the grafted polymer layer, in combination, constituting a modified surface having a fibrinogen adsorption of less than about 125 ng/cm2 in a fibrinogen binding assay in which the modified surface is incubated for 60 minutes at 37 C in 70 µg/mL fibrinogen derived from human plasma containing 1.4 µg/mL I-125 radiolabeled fibrinogen.
163 citations
TL;DR: The catalytic mechanism of metallo-beta-lactamase from Bacteroides fragilis, a dinuclear Zn(II)-containing enzyme responsible for multiple antibiotic resistance, has been investigated by using nitrocefin as a substrate, showing a novel anionic species bound to the enzyme through a Zn-acyl linkage and contains a negatively charged nitrogen leaving group.
Abstract: The catalytic mechanism of metallo-beta-lactamase from Bacteroides fragilis, a dinuclear Zn(II)-containing enzyme responsible for multiple antibiotic resistance, has been investigated by using nitrocefin as a substrate. Rapid-scanning and single-wavelength stopped-flow studies revealed the accumulation during turnover of an enzyme-bound intermediate with intense absorbance at 665 nm (epsilon = 30 000 M(-1) cm(-1)). The proposed minimum kinetic mechanism for the B. fragilis metallo-beta-lactamase-catalyzed nitrocefin hydrolysis [Wang, Z., and Benkovic, S. J. (1998) J. Biol. Chem. 273, 22402-22408] was confirmed, and more accurate kinetic parameters were obtained from computer simulations and fitting. The intermediate was shown to be a novel anionic species bound to the enzyme through a Zn-acyl linkage and contains a negatively charged nitrogen leaving group. This is the first time such an intermediate was observed in the catalytic cycle of a Zn(II)-containing hydrolase and is evidence for a unique beta-lactam hydrolysis mechanism in which the amine can leave as an anion; prior protonation is not required. The electrostatic interaction between the negatively charged intermediate and the positively charged dinuclear Zn(II) center of the enzyme is important for stabilization of the intermediate. The catalytic reaction was accelerated in the presence of exogenous nucleophiles or anions, and neither the product nor the enzyme was modified during turnover, indicating that a Zn-bound hydroxide (rather than Asp-103) is the active site nucleophile. On the basis of all the information on hand, a catalytic mechanism of the B. fragilis metallo-beta-lactamase is proposed.
163 citations
TL;DR: The crystal structure of the molybdenum enzyme dimethylsulphoxide reductase (DMSOR) has been determined at 1.9 A resolution with substrate bound at the active site and X-ray edge data indicate that the metal is in the Mo(IV) state.
163 citations