GLUCOSE-OXIDASE MEDIATION BY SOLUBLE AND IMMOBILIZED ELECTROACTIVE DETERGENTS

A series of novel, surface-active, inorganometallic complexes of osmiu m were synthesized and then characterized (using electrochemical techn iques) as electron transfer mediators for glucose oxidase (EC 1.1.3.4, GOD) from Aspergillus niger. The mediators contain a dipyridylamine l igand bearing (on the amine nitrogen) a saturated alkyl chain (typical ly C-5 to C-12), omega-terminated with either a methyl group or a func tional group such as carboxyl or hydroxyl. Such compounds displayed su btle differences in their interactions with GOD. The presence of a cc- functional group tended to diminish a mediator's micelle-forming activ ity, but also concomitantly decreased the denaturing action of the med iator towards the protein structure of GOD. However, the presence of a n ionised carboxyl group slowed GOD mediation relative to that of a si milar mediator bearing a methyl-terminated long alkyl chain, probably because of the additional negative charge. The omega-carboxyl function ality allowed covalent coupling of mediators to NH2-bearing graphite e lectrodes. GOD was co-immobilized and the resulting, reagentless, gluc ose-sensitive electrodes were characterized. Immobilization of the med iator did not appear to affect unduly the ability to mediate GOD. Addi tionally, complexes were directly coupled to lysine groups of GOD to g ive a self-mediating enzyme.