Glucose oxidase chemical modifications

All electrodes react with their environment via the surfaces in ways which will determine their electrochemical performance. Properly selected surface modification can effectively enhance the electrode heterogeneous catalysis property, especially selectivity and activity. The bulk materials can be chosen to provide mechanical, chemical, electrical, and structural integrity. In this part, several surface modification methods will be introduced in terms of metal film deposition, metal ion implantation, electrochemical activation, organic surface coating, nanoparticle deposition, glucose oxidase (GOx) enzyme-modified electrode, and DNA-modified electrode. 

Fig. 1.12. Schematb drawing of the glucose oxidase molecule, showing the electron-transfer distances involved in the various steps of moving an electron from its two flavin adenine dinucleotide/reduced flavin adenine dinucleotide (FAD/FADHg) centers to a metal electrode. Left The enzyme before modification. Right The modified enzyme, after chemical attachment of an array of electron transfer relays ( R ). (Reprinted from Y. Degani and A. Heller, J. Phys. Chem. 91 1286, 1987.)...

The mediators are bound to amino acids near the prosthetic group. For fixation of the relays the protein has to be unfolded and renatured after the chemical modification procedure. The small distance between the bound mediator molecules (maximum 1 nm) provides a very fast tunneling process. Enzyme electrodes employing glucose oxidase or lactate oxidase modified in this way operate like mediator-modified electrodes, without reagent addition. Owing to their favorable structure, such sensors respond to the analyte in less than... 

Glucose oxidase and D-amino acid oxidase can be chemically modified both in the presence and the absence of 2 M urea. At 2 M concentration urea interacts with proteins, opening their structure. Modification in the presence of 2 M urea was preferred because of superior reproducibility of the modified-enzyme-properties and because of superior electrochemical... 

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