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Cobalt Polypyridyl Complexes as Redox Mediators for Lipoamide Dehydrogenase
Author(s) -
Colón Carmen M.,
Guadalupe Ana R.
Publication year - 1998
Publication title -
electroanalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.574
H-Index - 128
eISSN - 1521-4109
pISSN - 1040-0397
DOI - 10.1002/(sici)1521-4109(199807)10:9<621::aid-elan621>3.0.co;2-m
Subject(s) - lactate dehydrogenase , chemistry , redox , dehydrogenase , cofactor , acetonitrile , cyclic voltammetry , cobalt , inorganic chemistry , electrochemistry , enzyme , biochemistry , organic chemistry , electrode
A series of cobalt polypyridyl complexes were synthesized and characterized by cyclic voltammetry in aqueous and acetonitrile solutions. Their mediation ability toward FADH 2 oxidation in a monoenzyme (lipoamide dehydrogenase) and a bienzyme (lipoamide dehydrogenase coupled to lactate dehydrogenase) system was studied. Of all the complexes tested, only the [Co(tpy) 2 ](PF 6 ) 2 , [Co(NH 2 ‐phen) 3 ](PF 6 ) 2 and [Co(CH 3 ‐phen) 3 ](PF 6 ) 2 showed a current enhancement indicative of an EC cat mechanism in the presence of lipoamide dehydrogenase and NADH. No cross reactivity was observed for these complexes in the presence of lactate dehydrogenase/ NAD + and lactate. The results also suggest that factors such as hydrophobic interactions, steric hindrance, H‐bonding and driving force are important when designing a redox mediator for a biosensor. Protein and/or cofactor adsorption fouled the electrode surface lowering the current response. A self‐contained bienzymatic biosensor exhibited a linear response (peak current versus log [lactate]) for lactate concentrations between 5 μM to 5 mM with a lowest detectable lactate concentration of 4.76 μM.