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LIGHT‐DRIVEN H 2 PRODUCTION WITH PROFLAVIN AND HYDROGENASE: COMPARISON OF CYTOCHROME C3 AND METHYL VIOLOGEN AS e ‐ MEDIATORS
Author(s) -
Eng Lars H.,
Lewin Mona B.M.,
Neujahr Halina Y.
Publication year - 1993
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1993.tb04938.x
Subject(s) - hydrogenase , chemistry , quenching (fluorescence) , photochemistry , redox , excited state , cytochrome , electron transport chain , enzyme , stereochemistry , medicinal chemistry , inorganic chemistry , biochemistry , fluorescence , physics , quantum mechanics , nuclear physics
We have studied the hydrogenase‐catalyzed production of H, when either its natural electron mediator cytochrome c 3 (c 3 ) or the artificial mediator methyl viologen (MV) was reduced by illumination of proflavin (PF) in the presence of ethylenediaminetetraacetate (EDTA). The reduction rates of MV and c 3 were comparable at equivalent concentrations of PF, taking into account the four redox sites of c 3 . However, when the concentration of c 3 exceeded that of PF, the reduction rate decreased. We explain this by light quenching. In the H 2 ‐producing system, MV was more efficient than c 3 as electron mediator when the initial reaction rates were compared. However, under certain conditions with MV, the rate of H 2 production decreased rapidly with time of illumination, whereas with c 3 it consistently remained stable. Possible reasons for this difference are discussed. Severe inactivation of hydrogenase was observed in the absence of the primary electron donor EDTA. It is concluded that this inactivation is caused by the excited state of PF