Achieving a unified understanding of the mechanism of a multi-center redox enzyme such as [NiFe] hydrogenase is complicated by difficulties in reconciling information obtained using different techniques, and on samples in different physical forms. Measurements of the activity of the enzyme, and of factors which perturb activity, are generally carried out using biochemical

Controlled formation of catalytically-relevant states within crystals of complex metalloenzymes represents a significant challenge to structure-function studies. Here we show how electrochemical control over single crystals of [NiFe] hydrogenase 1...