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Direct electrochemical oxidation of Clostridium pasteurianum ferredoxin
Author(s) -
Armstrong F.A.,
Hill H.A.O.,
Walton N.J.
Publication year - 1982
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(82)81337-9
Subject(s) - ferredoxin , electron transfer , chemistry , differential pulse voltammetry , pyrolytic carbon , electrochemistry , cluster (spacecraft) , redox , cyclic voltammetry , crystallography , photochemistry , electrode , inorganic chemistry , organic chemistry , pyrolysis , computer science , programming language , enzyme
Rapid oxidation processes relevant to the degradation of [4Fe‐4S] clusters in Clostridium pasteurianum ferredoxin were studied via direct (unmediated) heterogeneous electron transfer at a pyrolytic graphite electrode. Differential‐pulse voltammograms of native [4Fe‐4S] ferredoxin showed two well‐defined oxidation peaks corresponding to apparent E ‐values of +793 and +1120 mV at 5°C. Direct involvement of the cluster was established through parallel experiments with the 2[4Fe‐4Se] derivative for which peak positions were shifted. Square‐wave voltammetry showed that the product of the first electron transfer, which may correspond to the ‘super‐oxidised’ [4Fe‐4S] 3+ oxidation level, undergoes rapid degradation ( t ½ < 1.6 ms at 5°C). The second oxidation process, as characterised by a significant (⪢100 mV) negative shift upon selenium substitution, very likely represents oxidation of S(Se) still associated with the protein and possibly contained within the remaining FE‐S(Se) substructure.