Oxygen electrode assay method

Haga et al. developed another type of immunosensor by combining an enzyme membrane immunoassay and an enzyme sensor using oxygen electrodes (HI). In this assay antigen molecules (theophylline) are attached on the surface of the liposomes and an enzyme (horseradish peroxidase) is encapsulated in the sensitized liposome. When antibody (antitheophylline antibody) and complement are added, the enzyme is released by the liposome lysis. The enzyme activity with the NADH-NAD reaction can be determined by the oxygen electrode. When antigen is added, it competitively binds to antibodies, then liposome lysis and enzyme activity are decreased. The sensitivity of this method for theophylline determination was reported as 0.7 ng/ml. 

Two methods will be used to assay electron transport catalyzed by these Keilin-Hartree particles. In most of the experiments, an oxygen electrode will be used to measure the rate of oxygen consumption. Oxygen electrodes are described in the next paragraph. A spectrophotometric assay of electron transport will also be used. This assay re-... 

The most convenient assay of mitochondrial respiration and ATP synthesis is to measure the changes in oxygen consumption of intact isolated organelles after several additions of ADP with an oxygen electrode (Chance and Williams, 1956 Estabrook, 1967). In exactly the same way, but using much lower amounts of organelles, the HbOg method could... 

A number of assay methods have been used for measuring lipoxygenase. These techniques use radioisotopes or the oxygen electrode and colorimetric methods. These assays and necessary precautions are discussed by Galliard and Chan (1980). 

Callus cultures were established with three olive (Olea europaea L.) varieties using a method reported previously (2). Volatiles were collected from the olive cultures (20g) using dynamic headspace sampling techniques described previously (3). Analysis of volatiles was performed using an Automatic Thermal Desorption System linked to a Perkin Elmer Autosystem GC. Lipoxygenase (LOX) activity of the cultures was assayed routinely using an oxygen electrode. 

Bioassays. The biological activities of the synthetic peptides were determined using assay methods that were adapted to require only small amounts of peptide. Antifungal and antibacterial bioassays were performed in 96-well microtiter plates. Potential phytotoxicity was routinely evaluated using an oxygen electrode to measure inhibition of photosynthesis or respiration. All tests included magainin 1 or magainin 2 as a standard reference. Assay conditions were established to compare the relative activities of peptides, the absolute values cannot be extrapolated directly to activities in the field. 

Two principal methods are widely used for the assay of DPOs. For enzyme kinetic studies, the most appropriate methods are polarographic and use an 02 electrode (Basic Protocol), which allows the direct measurement of the rate of utilization of oxygen and a true comparison of different phenolic substrates. Minor disadvantages of this method are that it requires more specialized equipment and that assays can only be carried out one at a time. Nevertheless it has proven to be the basis of some excellent undeigraduate biochemical laboratory experiments. 

To create a fast and simple method for monitoring of human exposure to neuropathic OPs, a principal new approach to NTE activity analysis has been developed in joint study of the Institite of Physiologically Active Compounds Russian Acad. Sci. and Chemical Department of Moscow State University [88,91,92], Recently, a new biosensor for NTE assay was introduced using a tyrosinase carbon-paste electrode to detect phenol produced by the hydrolysis of phenyl valerate. In this type biosensor phenol is quantified by measuring electroreduction of the generated o-quinone on a graphite electrode (Fig. 6) [88,91 ]. The tyrosinase carbon-paste electrode improved the sensitivity of the NTE assay 10-fold compared to the colorimetric method or an earlier amperometric technique based on oxygen detection [92]. Moreover, the new electrode operates in a... 

Photosystem II preparations were isolated using the method of Berthold et al. (3). Salt-washed PSII membranes were obtained by exposing the PSII preparations to 2 M NaCl for 30 min. (dark) at 1.5 mg Chl/ml and washed once in MES buffer (pH 6.0). For reductant treatment, intact and salt-washed PSII preparations were incubated with a reductant in the dark for different periods of time (30 min. for intact and 3 min. for salt-washed) at 2 mg Chl/ml. Oxygen evolution was assayed in a Clark-type O2 electrode in 10 mM CaCl2 and 50 mM MES using 2,6-dichloro-p-benzoquinone as accepter. 

Polycyclic aromatic hydrocarbons (PAHs) belong to the group of compounds that in principle can be determined directly using ECL with the radical annihilation method. One practical drawback making the quantitative assay difficult is the sensitivity of the method to water and oxygen. However, ECL has been used as a detection system for reversed-phase LC with a mobile phase containing 10-20% water. ECL with oxide-coated electrodes has been used for the PAH assay in a micellar aqueous phase. 

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