| quinhydrone electrode | One of several oxidation-reduction electrode's in which the ratio of the two forms (quinone-quinhydrone), determined by the hydrogen ion concentration, sets up a potential that can be measured and converted to a pH value (fails above pH 8). (05 Mar 2000) |
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| ion selective electrode | An electrode half cell, with a semi permeable membrane that is permeable only to a single ion. The electrical potential measured between this and a reference half cell (e.g. A calomel electrode) is thus the Nernst potential for the ion. Given that the solution filling the ion selective electrode is known, the activity (rather than concentration) of the ion in the unknown solution can be measured. Commercial ion selective electrodes frequently use a hydrophobic membrane containing an ionophore, such as valinomycin (for potassium) or monensin (for sodium). A pH electrode is made with a thin membrane of pH sensitive (i.e. Proton permeable) glass. (18 Nov 1997) |
| oxidation-reduction electrode | An electrode capable of measuring oxidation-reduction potential. See: quinhydrone electrode. Synonym: redox electrode. (05 Mar 2000) |
| oxygen electrode | A sensitive method to detect oxygen consumption, involves a PTFE (Teflon) membrane. (18 Nov 1997) |
| therapeutic electrode | A small electrode whose exciting effect is used to stimulate or record potentials from a localised area. Synonym: exciting electrode, localizing electrode, therapeutic electrode. (05 Mar 2000) |
| electrode | <chemistry> Any terminal that conducts an electric current into or away from various conducting substances in a circuit (such as the anode or cathode of a battery). (09 Jan 1998) |
| electrode catheter ablation | A method of ablating the site of origin of arrhythmias whereby high energy electric shocks are delivered by intravascular catheters. (05 Mar 2000) |
| electrode knife | A blade-shaped electrical instrument used to cut tissues by means of a high-frequency electrical current. (05 Mar 2000) |
| exciting electrode | A small electrode whose exciting effect is used to stimulate or record potentials from a localised area. Synonym: exciting electrode, localizing electrode, therapeutic electrode. (05 Mar 2000) |
| exploring electrode | An electrode placed on or near an excitable tissue; in unipolar electrocardiography, the electrode is placed on the chest in the region of the heart and paired with an indifferent electrode. (05 Mar 2000) |
| localizing electrode | A small electrode whose exciting effect is used to stimulate or record potentials from a localised area. Synonym: exciting electrode, localizing electrode, therapeutic electrode. (05 Mar 2000) |
| acetyl-activating enzyme | A ligase that catalyses the reaction of acetate and CoA and ATP to form AMP, pyrophosphate, and acetyl-CoA. A key step in the activation of acetate. Synonym: acetate thiokinase, acetate-CoA ligase, acetyl-activating enzyme, acetyl-CoA synthetase. (05 Mar 2000) |
| acyl-activating enzyme | <enzyme> Fatty acid thiokinase (long-chain), a ligase forming acyl-CoA, AMP, and pyrophosphate from long-chain fatty acids, ATP, and coenzyme A. Activity is independent of phosphatidylcholine Registry number: EC 6.2.1.3 Synonym: acyl-activating enzyme, dodecanoyl-CoA synthetase, fatty acid thiokinase (long chain), acid-coenzyme a ligase, fatty acid-CoA ligase, acyl-CoA synthetase, acyl-CoA ligase, coash ligase, ciprofibroyl-CoA synthetase, pristanoyl-CoA synthetase, palmityl CoA synthetase, palmitoyl CoA synthetase, palmitoyl CoA ligase, fatty acyl-CoA synthetase, very long chain fatty acid acyl-CoA synthetase, vlcfa acyl-CoA synthetase, nafenopin-CoA ligase, palmitoyl-CoA synthase, faa2 gene product, faa2p protein, vlacs enzyme (26 Jun 1999) |
| adaptive enzyme | Inducible enzyme, an enzyme that can be detected in a growing culture of a microorganism, after the addition of a particular substance (inducer) to the culture medium, but was not detectable prior to the addition and can act on the inducer. A prototype is the beta-galactosidase of Escherichia coli, synthesised upon the addition of various galactosides, whether or not these are good substrates. Compare: constitutive enzyme. Synonym: adaptive enzyme. (05 Mar 2000) |
| allosteric enzyme | <biochemistry, chemistry> A regulatory enzyme whose activity is modified by the noncovalent binding of a particular metabolite at a site (the allosteric site) other than the active site. (09 Oct 1997) |