Malate sensor

Albareda-Sirvent and Hart [65] L-Malate, l-lactate Wines Lactate oxidase or malate dehydrogenase/in sol-gel matrix Sol-gel thick-film printed graphite electrode (contained NAD+ for malate sensors)/+ 350 mV vs. Ag/AgCl for lactate sensor and -125 mV vs. Ag/ AgCl for malate Meldola s Blue (mediator for the dehydrogenase)... 

Esti et al. [8] L-Lactate L-Malate Micro-malolactic fermentation in red wine Lactate oxidase/in a nylon membrane with glutaraldehyde or NAD(P)+-dependent l-malate dehydrogenase oxaloacetate decarboxylating/ immobilised in an aminopropyl glass beads reactor Platinum electrode/ +650mV vs. Ag/AgCl Phenazine methosulfate (for malate sensor)... 

Malate 1 x 10 5-10 4M Malate 3 x 10-6M acid) For malate sensor NADP+and... 

Qing G, He Y, Chen Z et al (2006) Sensitive fluorescent sensors for malate based on calix[4] arene bearing anthracene. Tetrahedron Asymmetry 17 3144—3151... 

Matsumoto et al (41) prepared a multi-enzyme electrode using glucose oxidase, invertase, mutarotase, fructose-5-dehydrogenase, and catalase to simultaneously detect glucose, fructose, and sucrose in fruit juices and soft drinks. Detection of multi-components by enzyme sensors was also reported in analysis of sucrose and glucose in honey (42) and drinks (43), and L-malate and L-lactate in wines (44). 

Fig. 86. Coupling of enzyme reactions for the design of a sensor family based on LMO. CK = creatine kinase, PK = pyruvate kinase, MDH = malate dehydrogenase, PEP = phosphoenolpyruvate, ALAT = alanine aminotransferase, ASAT = aspartate aminotransferase.

Using this reaction, Weigelt (1987) and Schubert et al. (1991) employed the LDH-LMO sensor for assaying ALAT and aspartate aminotransferase (ASAT, EC 2.6.1.1). For this purpose, malate dehydrogenase (MDH, EC 1.1.1.37) was additionally immobilized in the enzyme membrane. ALAT was determined as described above, and the ASAT reaction then initiated by substrate injection. MDH reduces the oxaloacetate formed to malate ... 

Burstein et al. (1986) have shown that in addition to induction and inhibition mechanical and chemical changes of the cell structure effect the selectivity of microbial sensors. Escherichia coli cells were treated by ultrasound, extrusion, or crosslinked with glutaraldehyde before used in sensors for D- and L-lactate, succinate, L-malate, 3-glycero-phosphate, pyruvate, NADH, and NAD PH. The treatment caused different selectivity of the respiratory chain and thus permitted an increase in the specificity of the respective sensors. 

Other metabolites that have been measured with calorimetric sensors include ascorbic acid, ATP/ADP (adenosine 5 -diphosphate), cephalosporins, galactose, hydrogen peroxide, lactose, malate, phospholipids, uric acid, xanthine, and hypoxanthine. 

When a solution containing variable amounts of malate and tartrate was added to the multicomponent sensor, a characteristic UV-Vis spectrum response was obtained. Since the different receptor-dye complexes and the free dyes all have different colors, the information about the analytes was dispersed over the entire spectrum. To analyze the spectral changes, a multilayer preceptron (MLP) artificial neural network (ANN) was employed (see Glossary in Box 7.1). To train the ANN, the UV-Vis absorption data of 45 calibration samples containing different amounts of malate and tartrate (0-1.2 mM) were used. For each sample, the absorbances at... 

Increasing the amount of enzyme attached to the surface will increase the amount of electrochemically detectable cofactor (e.g., NADH, H2O2) produced in the enzymatic reaction, up to a point. It has been shown for at least one system that the optimum maximum concentration of enzyme on the surface can clearly be reached [27]. In this work two enzymes, NADP -dependent L-malate dehydrogenase and p-hydroxybenzoate hydroxylase, were immobilized on a Clark electrode. The resulting bienzyme sensor behaved as if a single enzyme with a selectivity for L-malate was immobilized, and the optimal surface concentration for both enzymes was found to be approximately 5 U/cm. Furthermore, in order to fabricate a microelectrode with the fast time response necessary to measure neu-... 

With sensor 191 the binding of the tartrate or malate anions can be detected through the competitive displacement of alizarin complexone. The same sensor system was used for the analysis of malate in pinot noir grapes. When 192 was paired with pyrocatechol violet an assay suitable for the detection of gallic acid in Scotch whiskies was developed. An increase in the concentration of gallic acid correlated with the age of the whiskies. A combination of 191 and 192 and two indicators pyrocatechol violet and bromopyrogallol red can be used to detect the concentrations of tartrate and malate in mixtures. Using... 

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