Enzyme electrodes starch

YSI (Yellow Springs, OH, USA) Sugars, alcohols, starch Enzyme electrodes... 

Multienzyme tylon Electrodes. Di- and polysaccharides require more than one enzyme to realise the amperanetrically detectable hydrogen peroxide and even glucose really needs the back up of mutarotase with glucose oxidase. It is fortunate that all the necessary enzymes can be immobilized simultaneously on just one nylon net. Thus a viable starch electrode has been fabricated (6) from a nylon net immersed in a cocktail of glucose oxidase, mutarotase and amylogluoosidase (Figure 1). Its response to a continuous flow of 0.1% m/v starch remained steady for over a period of 60 h. 

Figure 1. The Accumulative Effects of 60Cb-Y Radiation on the Response of a Triple Enzyme Starch Electrode. Control 1.2 Mrad 2.4 Mrad 4.8 Mrad.

Acetylcholineesterase and choline oxidase Enzyme immobilized over tetra-thiafulvalene tetracyanoquinodi-methane crystals packed into a cavity at the tip of a carbon-fiber electrode. The immobilization matrix consisted of dialdehyde starch/glutaraldehyde, and the sensor was covered with an outer Nafion membrane. The ampero-metric performance of the sensor was studied with the use of FIA system. An applied potential of +100 mV versus SCE (Pt-wire auxiliary electrode) and a carrier flow rate of 1 mL/min. The Ch and ACh biosensors exhibited linear response upto 100 pM and 50 pM, respectively. Response times were 8.2 s. [97]... 

The formation of low-molecular weight products of the a-amylase-cat-alyzed starch hydrolysis can be assayed by using a glucoamylase-GOD electrode (Pfeiffer et al., 1980). The sensor is covered by a dialysis membrane with a cutoff of 15 kDa which prevents starch from reaching the enzymes. The cleavage products can easily diffuse into the bienzyme membrane where they are successively degraded to glucose by glu-coamylase. As only the (B-anomer is formed, the sensitivity of the method... 

Some time in 1968, Carter saw his first enzyme variants —beautiful little bands of sky blue on a China white gel (a flat slab of starch gel on a glass plate that had been laid between electrodes), each band at a precise and different position on the gel according to the strain of malaria parasite whose content had been extracted for electrophoretic separation (Carter, 1970). They were the biochemical genetic markers of two strains of Plasmodium berghei yoelii (as then defined), 17X and 33X that Walliker needed in order to be able to analyze a genetic cross between these two parasites. 

Determination of starch in a flow injection system using immobilized enzymes and a modifled electrode Anal. Chim. Acta 180 3-8... 

J. Emn6us, R. Appelqvist, G. Marko-Varga, L. Gorton, and G. Johansson, Determination of Starch in a Flow Injection System Using Immobilized Enzymes and a Modified Electrode. Anal. Chim. Acta, 180 (1986) 3. 

Fig.4. (top) Reaction scheme for the enzymatic determination of starch as executed in the FIA manifold shown below, where AMG refers to amyloglucosidase and GDH to glucose dehdrogenase, both of which enzymes are immobilized on porous glass in separate packed-bed reactors. The detection of the generated NADH is facilitated amperometrically by means of a modified electrode at 0 mV vs. Ag/AgCl, 0.1 M KCl. Flow rates are given in ml/min injected volume 30... 

Other applications of the technique include the use of immobilized glucose isomerase for the enrichment in fructose of corn starch hydrolysates and the use of immobilized pectinases for the clarification of fruit juice and wine. Immobilized enzymes have also been used as sensors for particular substrates. For example, a glucose-specific electrode has been developed which consists of glucose oxidase (page 94) entrapped in a polyacrylamide gel which is layered over a conventional polarographic oxygen electrode. 

Physical entrapment within an inert polymeric membrane (in this case the enzyme is mixed with a monomer solution, which is then polymerized to a gel - polyacrylamide gel, starch, agar gel, and so on, thus trapping the enzyme) or behind a membrane (in this case the enzyme solution is simply confined by an analyte permeable membrane, such as a dialysis membrane, as a thin film covering the indicator electrode this method is also called microencapsulation) ... 

The coreticulation described above [3] is simple to perform during multienzymatic immobilization. The required enzymes are mixed with albumin, and enough glutaraldehyde is added to cross-link the various proteins. This method is also used for the coimmobilization of creatinin amidohydrolase, creatin amidinohydrolase and sarcosine oxidase, to construct a creatinin electrode, and for the coimmobilization of a-glucosidase and glucose oxidase for the determination of starch [40]. 

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