Glucose oxidase Subject

The aldose (11.1 mmol) was dissolved in water to a final concentration of 0.5 m and subjected to oxidation by addition of glucose oxidase (200 mg, 400 U) and a large excess of catalase (1 mL, 25 kU). The mixture was vigorously stirred under air and the pH was kept constant at 7.5 by means of a pH-stat adding continuously 1 m NaOH. The conversion degree was directly calculated considering the volume of added 1 m NaOH, since 1 mol of NaOH neutralizes 1 mol of aldonic acid formed. 

Chemical analysis in which the masa is subjected to amyloglucosidase hydrolysis followed by the determination of glucose with glucose oxidase. The ESS assay corelates with degree of cooking and starch gelatinization. 

Key to electrical communication between glucose oxidase and the electrodes is the spacing, i.e., the density, of relays. The relays must be sufficiently close to both the FAD/FADH2 centers and to the metal electrodes (and possibly also to each other) for the electron transfer to be rapid. The distance-dependence of electron transfer rates in biosystems has been the subject of intensive theoretical and experimental research in recent years . It is now evident that for distances greater than 8 A electron transfer rates (k) within and between molecules, as well as between electrodes and ions or molecules in their proximity, or between the ions themselves, decay exponentially with the distance (d) between the involved centers, i.e., k = In proteins the electron... 

As a rule, the combined immobilization of oxidase and peroxidase on the electrode allows the determination of metabolite (S) concentration, even if negligibly small. This type of biosensor is the main one used for detection of any particular compound in blood or other multicomponent system glucose, ethanol, cholesterol, proteins, amino acids, etc. For example, for patients with diabetes a rapid analysis of their blood for glucose concentration is a vitally important procedure. We will not attempt to discuss in full all the existing types of biosensor we will just note that enzymatic and cell biosensors are the most widespread types of these appliances. Enzymatic biosensors are more appropriate to the subject of the current monograph and, therefore, they will be discussed below. 

Like glutathione reductase, pyridoxine oxidase is sensitive to riboflavin depletion. In normal subjects and in experimental animals, the EGR and pyridoxine oxidase activation coefficients are correlated, and both reflect riboflavin nutritional status. In subjects with glucose 6-phosphate dehydrogenase deficiency, there is an apparent protection of EGR, so that even in riboflavin deficiency it does not lose its cofactor, and the EGR activation coefficient remains within the normal range. The mechanism of this protection is unknown. In such subjects, the erythrocyte pyridoxine oxidase activation coefficient gives a response that mirrors riboflavin nutritional status (Clements and Anderson, 1980). 

In addition to the previously described dehydrogenase-based CNT electrodes, electrochemical biosensors that employ other types of enzyme-modified CNTs have also been reported. Kowalewska and Kulesza applied CNTs with adsorbed redox mediator tetrathiafulvalene (TTF) for electrochemical detection of glucose." TTF-modified CNTs were found to facilitate electron transfer between GOx and the electrode surface for glucose detection. Jia et al. reported a similar strategy for the detection of lactate using MWCNTs modified with TTF and lactate oxidase. Since TTF does not cause skin irritation and the CNT/TTF platform also enables low-potential sensing of lactate, CNT/ TTF/lactate oxidase-based electrochemical biosensors conld be used to detect lactate in perspiration directly on human skin. This was accomplished by preparing temporary tattoos from CNT/ TTF/lactate oxidase-conductive carbon ink that was transferred onto a human subject s skin. ... 

---