Glucose oxidase, investigated

On the basis of the knowledge that different polyelectrolytes can stabilize proteins [180], even in water-organic mixtures [181], it was important to check the membraneforming polyelectrolyte itself as a potential stabilizer. Indeed, as was found from spec-trophotometric investigations, Nation stabilizes glucose oxidase suspensions in organic solvents. 

Enzyme containing Nation membranes prepared according to the proposed protocol have shown high specific activity and stability of immobilized glucose oxidase. As expected, the simplicity of preparation provided high reproducibility. When the same casting solution is used, the maximum deviation in membrane activity is <2%. This, however, is also the precision limit for kinetic investigations. 

Apart from electron promoters a large number of electron mediators have long been investigated to make redox enzymes electrochemically active on the electrode surface. In the line of this research electron mediators such as ferrocene and its derivatives have successfully been incorporated into an enzyme sensor for glucose [3]. The mediator was easily accessible to both glucose oxidase and an electron tunnelling pathway could be formed within the enzyme molecule [4]. The present authors [5,6] and Lowe and Foulds [7] used a conducting polymer as a molecular wire to connect a redox enzyme molecule to the electrode surface. 

Glucose oxidase was first adsorbed onto the platinum surface at a controlled potential. The protein adsorption varied depending on several factors as electrode potential, glucose oxidase concentration, pH and temperature. The effects of these factors on protein adsorption were carefully investigated. 

Specific recognition of enzymes by their natural substrates and cosubstrates is a common rule but what about recognition of an enzyme by artificial cosubstrate The cyclic voltammetric investigation of glucose oxidase provides an answer to the question.11 Because the flavin prosthetic group... 

The feasibility of amperometric sucrose and mercury biosensors based on the immobilization of invertase, glucose oxidase, and muta-rotase entrapped in a clay matrix (laponite) was investigated by Mohammadi et al. [31]. In this work, the effect of pH of a tri-enzymatic biosensor in which the optimum pH of the three enzymes is different (Invertase, pH 4.5 Glucose oxidase, pH 5.5 and Mutarotase, pH 7.4) [41] was studied. The pH effect on the biosensor response was analyzed between pH 4 and 8 and the highest activity was found at pH 6.0. In order to improve the selectivity of the invertase toward mercury and to avoid silver interference, a medium exchange technique was carried out. The biosensor was exposed to mercury in an acetate buffer solution at pH 4 while the residual activity was evaluated with phosphate buffer solution at pH 6 [41]. 

The effect of the inhibitor in glucose oxidase biosensor response was investigated. The biosensor was incubated for 10 min in the presence of different concentrations of methyl mercury. It was seen that after exposure to the high concentration equal to 1 ppm of methyl mercury the response of glucose remained constant (results not shown). 

Huang Y, Zhang W, Xiao H, Li G. An electrochemical investigation of glucose oxidase at a CdS nanoparticle modified electrode. Biosensors Bioelectronics 2005, 21, 817-821. 

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