Relative CH4 concentrations determined after a 40 min
incubation of N2-saturated samples containing 10 μM
quinone, 100 μM DETAPAC, 100 μM neocuproine, 10 mM ascorbate,
and 2 mM H2O2 in 1:3 DMSO/phosphate buffer (20
mM, pH 7.4) (v/v). The symbols used to represent a blank sample without
quinone, PHQH2, and Fe2+ are for solutions without
quinone, with 10 μM PHQH2, or with 10 μM FeCl2, respectively, and correspond to the methane concentration,
but not to the one-electron reduction potential, indicated by the
position of the symbol. DETAPAC and neocuproine were not included
in samples with FeCl2. The symbols ascribed to PHQ correspond
to the same sample composition as that listed (■), with 10
μM DFO added (▲), or with 100 μM bathophenanthroline
disulfonate and 100 μM ferrozine added (▼).