Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:1.11.1.7 (peroxidase)
65,474 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A choline oxidase-peroxidase coupled enzyme procedures is proposed for the determination of cholinesterase activity in human serum. This system is not only kinetic and colorimetric but is also relatively quick and simple to perform. The initial comparisons suggest that this method correlates well with a commonly used propionylthiocholine-dinitrobis-(nitro-benzoic acid) technique. Large amounts of bilirubin in the sample appear to have only minor deleterious effects on the assay. Since there are only two reagents that may be premixed, the procedure appears to be amenable to automation. The use of a mixture of sodium 2-hydroxy-3,5-dichlorobenzenesulfonate and 4-aminoantipyrene in the peroxidase catalyzed indicator reaction provides for a marked increase in sensitivity over previously reported 4-aminoantipyrene-phenol systems. This augmented sensitivity provides for a relatively large reagent to sample ratio. In addition, the reagents lend themselves toward lyophilization or "dry-fill".
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PMID:A procedure for the kinetic colorimetric determination of serum cholinesterase activity. 713 38

Amperometric microsensors for the detection of choline in the extracellular fluid of brain tissue have been prepared by immobilizing horseradish peroxidase and choline oxidase onto carbon fiber microcylinder electrodes with a cross-linkable redox polymer. The microcylinders have diameters of 7 or 10 microns and lengths of 200-400 microns. To detect choline, the microsensors are operated at an applied potential of -0.1 V vs SCE. At this potential, ascorbate and other easily oxidizable interferant molecules present in brain tissue are not detected by the electrode. Ascorbate, however, can interfere with the response to choline by acting as a reducing agent in the enzyme-containing polymer film. So, a Nafion overlayer is required in order to reliably detect choline in the presence of physiologically relevant concentrations of ascorbate (approximately 200 microM). The Nafion-coated microsensors have a detection limit of approximately 5 microM choline and give a linear response beyond 100 microM when calibrated in vitro at 37 degrees C. Exposure of the microsensors to brain tissue for several hours causes less than a 10% loss in redox polymer surface coverage and less than a 25% loss in sensitivity to choline. To assess the ability of the microsensors to monitor choline levels in brain tissue, small volumes of a choline solution were injected into brain tissue at a site about 1 mm away from a microsensor. The current arising at the microsensor was converted to choline concentration by calibrating the sensor following the in vivo experiment. The resultant choline concentrations were in excellent agreement with those predicted by appropriate diffusion equations.
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PMID:Quantitation of choline in the extracellular fluid of brain tissue with amperometric microsensors. 794 33

Acetylcholine and choline chemiluminescent assays have limitations when these compounds are detected in small areas of mammalian nervous tissue. Use of 7-dimethyl-aminonaphthalene-1,2-dicarbonic acid hydrazide (7-DMAN), instead of luminol, gives a threefold increase in emitted light in the chemiluminescent assay for acetylcholine based on the coupled choline oxidase-peroxidase reaction. Addition of light enhancers, such as para-iodophenol or D-luciferin, to luminol or 7-DMAN further increased the light emission. Under these conditions the detection limit for acetylcholine was 650 femtomoles. This enhanced chemiluminescent assay should be convenient for the detection of in vivo and in vitro acetylcholine release from mammalian neurons.
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PMID:Enhanced chemiluminescent assays for acetylcholine. 802 5

A micro method is described for the assay of choline-containing phospholipids in serum and high density lipoproteins (HDL) using an automated microtiter plate reader. The method is adapted from the enzymic method of Takayama, Itoh, Nagasaki, and Tanimuzu (Clin. Chim. Acta 79, 93-98, 1977) using phospholipase D, choline oxidase, and peroxidase coupled with the color generating system phenol and 4-amino-antipyrine. The micro method requires 5 microL of serum or HDL sample, and 42 samples can be assayed in duplicate in one run using a 96-well flat-bottom microtiter plate. The reaction is linear up to 400 mg/dL and the lower limit of detection is 0.25 mg of choline-containing phospholipids per assay. The coefficient of variation within an assay is 0.86-0.79%, and day-to-day variation is 0.9-1.5%. Results obtained by the micro method are in excellent agreement with those obtained by the procedure of Takayama et al. (r = 0.997). The supernatant left after removal of low density lipoproteins and very low density lipoproteins from serum and precipitation with heparin/manganese chloride reagent can thus be conveniently used for the micro assay of choline phospholipids in HDL.
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PMID:A micro enzymic method for determination of choline-containing phospholipids in serum and high density lipoproteins. 824 95

Amperometric sensors have been developed for hydrogen peroxide, choline, and acetylcholine by immobilization of horseradish peroxidase, (HRP), choline oxidase, and acetylcholinesterase in a cross-linked redox polymer deposited on glassy carbon electrodes. Peroxide sensors, prepared by immobilization of HRP alone, gave detection limits of 10 nM and a linear response up to ca. 1 mM. Coimmobilization of HRP and glucose oxidase was used to establish the feasibility of highly efficient bienzyme sensors at low substrate levels. Replacing glucose oxidase with choline oxidase produced sensors with submicromolar detection limits and a linear response up to 0.8 mM. Addition of acetylcholinesterase to the sensors generated a relatively small response to acetylcholine that demonstrates the feasibility of trienzyme sensors. At low substrate concentrations, no loss in sensitivity during a 1-day experiment was observed. The response times of these sensors are all less than 30 s with 2-s response times achieved in some cases.
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PMID:Amperometric sensors for peroxide, choline, and acetylcholine based on electron transfer between horseradish peroxidase and a redox polymer. 845 44

A liquid chromatography-electrochemistry (LC-EC) method is described for the determination of basal acetylcholine (ACh) in microdialysate from the striatum of freely moving rats. This method is based on the separation of ACh and choline (Ch) by microbore liquid chromatography followed by passage of the effluent through a post-column immobilized enzyme reactor (IMER), containing acetylcholinesterase (AChE) and choline oxidase (ChO), and then the electrochemical detection of the hydrogen peroxide produced. Instead of the conventional platinum electrode generally used for the anodic detection of hydrogen peroxide, a peroxidase-redox polymer modified glassy carbon electrode operated at + 100 mV vs. Ag/AgCl has been used to detect the reduction of hydrogen peroxide. With this method, a detection limit of 10 fmol (injected) for ACh (S/N = 3:1) was obtained and the basal ACh concentration in striatal microdialysate was determined without using esterase inhibitors.
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PMID:Detection of basal acetylcholine in rat brain microdialysate. 854 23

A potentiometric method for cholinesterase inhibitor analysis based on mediatorless bioelectrocatalysis has been developed. The method includes coimmobilization of three enzymes, butyrylcholinesterase, choline oxidase and peroxidase, on composite carbon electrodes. Catalytic hydrolysis of butyrylcholine and subsequent catalytic oxidation of choline result in the formation of hydrogen peroxide leads to a shift in the electrode potential. The detection limit for trichlorfon analysis is 2 x 10(-13) M. Electrodes remain stable for at least 4 weeks when stored at 277 K.
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PMID:Potentiometric biosensors for cholinesterase inhibitor analysis based on mediatorless bioelectrocatalysis. 868 64

To determine the basal acetylcholine level in the dialysate of rat frontal cortex, a horseradish peroxidase-osmium redox polymer-modified glassy carbon electrode (HRP-GCE) was employed instead of the conventional platinum electrode used in high-performance liquid chromatography-electrochemical detection (HPLC-ED). In initial experiments, an oxidizable unknown compound interfered with the detection of basal acetylcholine release on HPLC-HRP-GCE. An immobilized peroxidase-choline oxidase precolumn (pre-reactor) was included in the HPLC system, to eliminate the interference from the unknown compound. This combination could detect less than 10 fmol of standard acetylcholine and basal acetylcholine levels in the dialysate from a conventional concentric design microdialysis probe, without the use of cholinesterase inhibitor, and may facilitate physiological investigation of cholinergic neuronal activity in the central nervous system.
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PMID:Detection of basal acetylcholine release in the microdialysis of rat frontal cortex by high-performance liquid chromatography using a horseradish peroxidase-osmium redox polymer electrode with pre-enzyme reactor. 883 37

Selective amperometric enzyme microsensors for monitoring low micromolar concentrations of choline in extracellular fluid of rat brain have been developed. Preparation of the choline microsensors involved the modification of carbon fiber microcylinder electrodes (10 microns diameter, 300-400 microns long) with a cross-linked redox-active gel containing horseradish peroxidase and choline oxidase. Rejection of the noise recorded from the choline microsensors implanted in living brain tissue improved the in vivo detection capabilities of the sensors. The microsensors and a differential detection scheme were used to estimate the basal concentration of choline in striatal tissue at 6.6 +/- 2.9 microM and to measure changes in choline concentrations of 6.1 +/- 2.7 microM in vivo. The microsensors were also used to monitor choline produced following the injections of acetylcholine in vivo. Coinjections of neostigmine and acetylcholine significantly lowered the choline response recorded with the microsensors, confirming that the response following the injections of acetylcholine alone was due to the activity of endogenous acetylcholinesterase. Comparison of the maximal rate of decrease in choline concentration following the injections of 1 mM choline and 1 mM acetylcholine was used to estimate the rate of acetylcholine clearance from extracellular fluid through cholinesterase activity at approx. 2.5 microM/min.
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PMID:Amperometric microsensors for monitoring choline in the extracellular fluid of brain. 898 84

Lipophilic, alkylated cyclodextrins (CDs) are aromatic hosts which are excellent ionophores for reversibly binding size-matched, charge-diffuse cations. The application of lipophilic beta-CDs as ionophores for sensing acetylcholine chloride using a potentiometric ISE and an amperometric biosensor is described. Potentiometric ISEs, using 2,6-didodecyl-beta-CD as ionophore, showed a Nernstian response with a limit of detection -log[C] = 5.0 and selectivity coefficient -logKijPot = 4.2 (in serum levels of Na+, K+ and Ca2+). A Nernstian response is maintained in the presence of bovine serum albumin for a PVC- and a polyurethane-based electroactive membrane on initial contact. However, on prolonged contact, the polyurethane-based membranes showed a lower shift in Einitial0 (the bias potential on initial contact with analyte solution) than PVC. Amperometric biosensors were assembled by modifying screen-printed electrodes with a ferrocenyl charge shuttle, enzymes (horseradish peroxidase, choline oxidase and/or acetylcholine esterase) and a thin film comprising a polyurethane matrix, 2,3,6-triethyl-beta-CD, a plasticizer and a large anionic salt. The resulting sensor, which was capable of detecting subpicomolar levels of acetylcholine, was highly specific and was stable to storage in air and in solution. Interference from endogenous electroactive compounds was minimal.
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PMID:Sensitive and specific electrochemical sensors for charge-diffuse cations: use of lipophilic cyclodextrins and an enzyme relay for the determination of acetylcholine. 900 5


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