Electrochemical potential-step investigations of the aerobic interconversions of [NiFe]-hydrogenase from Allochromatium vinosum: insights into the puzzling difference between unready and ready oxidized inactive states.

Dynamic electrochemical studies, incorporating catalytic voltammetry and detailed potential-step manipulations, provide compelling evidence that the oxidized inactive state of [NiFe]-hydrogenases termed Unready (or Ni-A) contains a product of partial reduction of O(2) that is trapped in the active site.