ABSTRACT
These results have been corroborated by stopped-flow studies under selective conditions, using Ru(NH3)63+ or Fe(CN)63− as oxidants [61]. The rate of oxidation of the protonated [3Fe-4S]0 cluster in the D15N variant is always slow and pH independent; whereas with native FdI, oxidation is fast and occurs at a rate constant that decreases as the pH is lowered. In all cases the kinetics are independent of the nature of the oxidant, and replacement of H2O by D2O reveals only a small isotope effect, showing that proton tunneling is not rate limiting.
