Biphenol as an Electron Transfer Mediator for Glucose Oxidase
- 1 August 1994
- journal article
- research article
- Published by Taylor & Francis in Analytical Letters
- Vol. 27 (11) , 2039-2053
- https://doi.org/10.1080/00032719408007233
Abstract
Biphenol (4,4′-dihydroxy-biphenyl) was found to be an electron transfer mediator for glucose oxidase (GOD) of Aspergillus niger. At a glassy carbon electrode, a 1.44×10-4 M solution of biphenol in phosphate-buffered saline (PBS) at pH 7.4 gives an quasi-reversible, one-electron, pH-sensitive couple at 255mV (relative to the standard calomel electrode). The apparent second-order rate constant for electron transfer from reduced GOD to oxidized biphenol was determined to be 3×105 M-1 s-1. When biphenol and GOD are cophysiadsorbed on a graphite electrode immersed in PBS and held at 400mV, a glucose-dependent current response is noted. In addition to the predominant quasi-reversible biphenol redox couple, repetitive cyclic voltammetry at a graphite electrode gave rise to a polybiphenol polymer; this is most marked at a pH above the biphenol pKa of about 9.5. At pH 7.4, the polymerization is less significant. Polybiphenol formed either side of the pKa remains electrochemically active (E°app. = 245mV) but no longer mediates GOD.Keywords
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