Enzyme electrode, for

A compound which is a good choice for an artificial electron relay is one which can reach the reduced FADH2 active site, undergo fast electron transfer, and then transport the electrons to the electrodes as rapidly as possible. Electron-transport rate studies have been done for an enzyme electrode for glucose (G) using interdigitated array electrodes (41). The following mechanism for redox reactions in osmium polymer—GOD biosensor films has... 

Enzyme electrodes for other substrates of analytical significance have been developed. Representative examples are listed in Table 6-1. Further advances in enzyme technology, and particularly the isolation of new and more stable enzymes, should enhance the development of new biocatalytic sensors. New opportunities (particularly assays of new environments or monitoring of hydrophobic analytes) derive from the finding that enzymes can maintain then biocatalytic activity in organic solvents (31,32). 

Hydrolase enzymes catalyze the hydrolysis of a substrate and are most commonly coupled with potentiometericela trodes The pioneering work in this field focussed on de loping an enzyme electrode for the determination of urea. Urease catalyzes the hydrolysis of urea to ammonium and bicarbonate ions according to the reaction detailed below. 

Enzyme electrodes for the amino acids tyrosine and lysine have been... 

Bilitewski U Jaeger A Rueger P., Weise W., Enzyme electrodes for the determination of carboghydrates in food, Sensor Actuat B-Chem. 1993 15(1-3) 113-118. 

G. Guilbault and G. Lubrano, An enzyme electrode for the amperometric determination of glucose. Anal. Chim. Acta 64, 439-455 (1973). 

A. Cass, G. Davis, G. Francis, H.A. Hill, W. Aston, J. Higgins, E. Plotkin, L. Scott, and A.P. Turner, Ferrocene-mediated enzyme electrode for amperometric determination of glucose. Anal. Chem. 56, 667-671 (1984). 

J. Wang and F. Lu, Oxygen-rich oxidase enzyme electrodes for operation in oxygen-free solutions. J. Am. Chem. Soc. 120, 1048-1050 (1998). 

J. Wang and X. Zhang, Screen printed cupric-hexacyanoferrate modified carbon enzyme electrode for single-use glucose measurements. Anal. Lett. 32, 1739-1749 (1999). 

B. Wang and S.J. Dong, Organic-phase enzyme electrode for phenolic determination based on a functionalized sol-gel composite. J. Electroanal. Chem. 487, 45-50 (2000). 

J.G. Zhao, J.R O Daly, R.W. Henkens, J. Stonehuemer, and A.L. Crumbliss, Axanthine oxidase/colloi-dal gold enzyme electrode for amperometric biosensor applications. Biosens. Bioelectron. 11, 493—502 (1996). 

C.L. Wang and A. Mulchandani, Ferrocene-conjugated polyaniline-modified enzyme electrodes for determination of peroxides in organic media. Anal. Chem. 67, 1109-1114 (1995). 

Hydrogen consumption Hydrogen enzyme electrode for fuel cells. 

Hall GF, Best DJ, Turner APF. 1988. Amperometric enzyme electrode for thedetermination of phenols in chloroform. Enzyme Microb Technol 10(9) 543- 546. 

The classic potentiometric enzyme electrode is a combination of an ion-selective electrode-based sensor and an immobilized (insolubilized) enzyme. Few of the many enzyme electrodes based on potentiometric ion- and gas-selective membrane electrode transducers have been included in commercially available instruments for routine measurements of biomolecules in complex samples such as blood, urine or bioreactor media. The main practical limitation of potentiometric enzyme electrodes for this purpose is their poor selectivity, which does not arise from the biocatalytic reaction, but from the response of the base ion or gas transducer to endogenous ionic and gaseous species in the sample. 

Fig. 6.27 Schematic of potentiometric enzyme electrode for urea, based on ammonium ion-selective electrode...

The choice of the ion sensor clearly depends on the type of the enzymatic reaction, namely on the products and reagents of that reaction and on the conditions of the sample. Thus, for example, there are several possibilities of the choice of the ion sensor for enzyme electrode for urea. 

The three types of glucose electrode discussed here illustrate the major facets of design and operation of enzymatic amperometric sensors. Examples of amperometric enzyme electrodes for other substrates are shown in Table 7.3. The actual design details of these sensors depend on the enzyme kinetics involved and on the operating conditions under which they are used. 

R.R. Walters, P.A. Johnson and R.P. Buck, Histidine ammonia-lyase enzyme electrode for determination of L-histidine, Anal. Chem., 52 (1980) 1684-1690. 

A. Lupu, D. Compagnone and G. Palleschi, Screen-printed enzyme electrodes for the detection of marker analytes during winemaking, Anal. Chim. Acta, 513(1) (2004) 67-72. 

S. Han, M. Zhu, Z. Yuan and X. Li, A methylene blue-mediated enzyme electrode for the determination of trace mercury (II), mercury (I), methylmercury, and mercury-glutathione complex, Biosens. Bioelectr., 16 (2001) 9-16. 

J. Diehl-Faxon, A.L. Ghindilis, P. Atanasov and E. Wilkins, Direct electron transfer-based tri-enzyme electrode for monitoring of organophos-phorus pesticides, Sens. Actuat. B. Chem., 36 (1996) 448-457. 

D. Moscone, Prussian Blue and enzyme bulk-modified screen-printed electrodes for hydrogen peroxide and glucose determination with improved storage and operational stability, Anal. Chim. Acta, 485 (2003) 111-120. A. Lupu, D. Compagnone and G. Palleschi, Screen-printed enzyme electrodes for the detection of marker analytes during winemaking, Anal. Chim. Acta, 513 (2004) 67-72. 

M. Kyrolainen, H. Hakanson, B. Mattiasson and P. Vadgama, Minimal fouling enzyme electrode for continuous flow measurement of whole blood lactate, Biosens. Bioelectron., 11 (1997) 1073-1081. 

The gas-sensing electrodes also are used for the potentiometric measurement of biologically important species. An enzyme is immobilized at or near the gas probe. The gas sensor measures the amount of characteristic gas produced by the reaction of the analyzed substance with the enzyme. For example, an enzyme electrode for urea [NH2C(0)NH2] determination is constructed by the immobilization of urease onto the surface of an ammonia-selective electrode. When the electrode is inserted into a solution that contains urea, the enzyme catalyzes its conversion to ammonia ... 

Enzyme electrodes for other substrates of analytical significance have been developed. Representative examples are listed in Table 6.1. Further advances in enzyme technology, particularly the isolation of new and more stable... 

Oxygen can be replaced by other (natural and synthetic) electron acceptors. The enzyme is widely applied in - biosensors, such as - enzyme electrodes, for the quantitative determination of /3-D-glucose in body fluids. See also - glucose sensors. 

The enzyme electrodes for determining uric acid monitor reactants or products of the uricase catalyzed reaction ... 

Enzyme electrodes for choline and acetylcholine (300, 301) and for the analysis of choline-containing phospholipids (303, 304) is obtained by immobilizing choline oxidase or choline oxidase and acetylcholinesterase on membranes at the tip of platinum electrodes. The formation of hydrogen peroxide is monitored ... 

In another advance in the use of immobilized enzymes in analysis, glucose oxidase was combined with an oxygen electrode to give an enzyme electrode for determining glucose concentration (15, 16). The... 

Figure 2. An enzyme electrode for determining glucose concentration...

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