| Abstract
| - A series of glucose oxidase (GOx) hybrids (GOx−phenothiazine-labeled poly(ethylene oxide) (PT-PEO)) capable of direct electrical communication with electrodesis synthesized by covalently modifying PT-PEO to lysineresidues on the enzyme surface. The length of the PEOchain and the number of PT groups are systematicallyaltered. After the PT-PEO modification, all the hybridsmaintain more than 50% of enzyme activity relative to thatof native GOx, although loss of the activity becomesgreater with increasing PEO chain length. The catalyticcurrent, icat, is observed at a potential more positive than0.55 V after the addition of glucose, due to the intramolecular electron transfer (ET) from reduced forms of flavinadenine dinucletide (FADH2/FADH) to PT+ that areelectrogenerated at the electrode. The icat value increaseswith the number of PT groups, indicating that most of themodified PT groups act as mediators. The magnitude ofthe icat increase depends on the PEO chain length andreveals a maximum for PT-PEO with the molecular weightof 3000. In contrast, the icat is almost constant for GOx−2-(10-phenothiazyl)propionic acid (PT-PA) hybrids withmore than two PT groups synthesized by covalentlymodifying PT-PA to surface lysines, indicating that only afew key PT groups function as mediators. The maximumrate constant (130 s-1) for the ET from FADH2/FADH toPT+ is obtained for the GOx hybrid modified with fivePT-PEO groups with the molecular weight of 3000.
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