Bioelectronic sniffer device for trimethylamine vapor using flavin containing monooxygenase

A bioelectronic sniffer device for trimethylamine (TMA) in the gas phase "fish-odor substance" was constructed using a flavin-containing monooxygenase 3 (FMO3, one of xeno-biotic metabolizing enzymes) and a reaction unit with both gas and liquid cells separated by a porous poly(tetrafluoroethylene) diaphragm membrane (pore size: 30-60 /spl mu/m, thickness: 0.20 mm). A substrate regeneration cycle was applied to the FMO3 immobilized device in order to amplify the output signal by coupling the monooxygenase with a reducing reagent system of ascorbic acid (ASA) in phosphate buffer. The sniffer device with 10.0 mmol/l AsA could be used to measure TMA vapor from 0.52 to 105 ppm; this covers the maximum permissible concentration in the work place (5.0 ppm of time weighted average concentration) and the sensing level-5 of smell in humans (3.0 ppm). Since the application of the substrate regeneration cycle was possibly successful, it improved the sensitivity of the FMO3 immobilized device. The sniffer device possessed high selectivity for TMA being attributable to the FMO3 substrate specificity, continuous measurability, and good reproducibility in the repeatedly measurements (coefficient of variation = 2.41%, n=10).     

Development of a microconductometric biosniffer for detection of trimethylamine

The paper describes the development of a conductometric biosensor for detecting trimethylamine (TMA) which is a good parameter for estimating fish freshness. The biosensor consists of two parts: a microconductometric transducer and a structured enzymatic membrane using a flavin-containing monooxygenase 3 (FMO3) which is known for its sensitivity and selectivity for TMA. The process parameters for the fabrication of the biosniffer and various experimental variables such as pH, time of exposure to glutaraldehyde vapour were investigated with regard to their influence on sensitivity and limit of detection. A low detection limit of 2 μg/mL (ppm) and a linear range up to 40 μg/mL (ppm) were obtained. 90% response was reached in less than 10 min.     

An optical flow injection analysis system for measurement of glucose in tomato

An optical flow injection analysis (FIA) system for glucose measurement in tomato was constructed by using a glucose oxidase (GOD) immobilized reactor and a photodiode sensor, a peristaltic pump and a personal computer. The GOD reactor was crammed with strip-shaped of a GOD immobilized membrane to an acrylic pipe. The GOD was immobilized on polytetrafluoroethylene membrane by crosslinking with glutaraldehyde. Hydrogen peroxide generated by the GOD reaction oxidized luminol to produce chemiluminescence in the presence of horseradish peroxide. The chemiluminescence was detected by using the photodiode. The glucose measurement system was calibrated with standard glucose solutions. The calibration range of the system for glucose was 2.0–100.0 mmol L⁻¹. Measurement time for every sample was within 3 min. Glucose concentrations of a fresh and processed tomato samples measured with this glucose measurement system could be evaluated rapidly and non-laboriously.     

Effects of quaternary ammonium compounds with 0.1% sodium hydroxide on swine vesicular disease virus

The purpose of the present study was to evaluate the role of central alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA)/kainate type of glutamate receptors in the control of ACTH and corticosterone release under basal and stress conditions. AMPA/ kainate competitive receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX), which does not penetrate the blood-brain barrier, was administered intracerebroventricularly (i.c.v.). A modified method for i.c.v. drug administration in conscious freely moving rats was employed. DNQX or artificial cerebrospinal fluid (aCSF) was injected into lateral ventricle through a thin polyethylene cannula with a steel needle on the end which was inserted and moved via large polyethylene cannula to the guide stainless steel cannula. This procedure was performed out of the cage. ACTH and corticosterone release under basal conditions and during immobilization stress were investigated. Intracerebroventricular administration of DNQX resulted in an increase of ACTH and corticosterone in plasma reaching maximal values at 15 min after drug injection. During immobilization stress, i.c.v. DNQX induced a mild reduction in plasma ACTH levels compared to those in aCSF pretreated rats. Corticosterone secretion was high throughout the whole period of stress exposure. These findings indicate that endogenous excitatory amino acids (EAA) acting at AMPA/kainate receptors may interfere with the control of ACTH release under both basal and stress conditions, but the mechanisms involved remain to be elucidated.