Sensitivity-enhanced magnetic resonance reveals hydrogen intermediates during active [Fe]-hydrogenase catalysis

Molecular hydrogen (H 2 ) is considered an eco-friendly future energy-carrier and an alternative to fossil fuel 1 and thus, major efforts are directed towards identifying efficient and economical hydrogen catalysts. 2,3 Efficient hydrogen catalysis is used by many microorganisms, some of them producing H 2 from organic materials and others consuming it. 4-6 To metabolize H 2 , these microorganisms use enzymes called hydrogenases. 7,8 For the future development of efficient catalysts a detailed analysis of the catalytic mechanisms of such hydrogenases is required and existing analytical techniques could not provide a full understanding. 9 Consequently, new analytical technologies are of utmost importance to unravel natures’ blueprints for highly efficient hydrogen catalysts. Here, we introduce signal-enhanced or hyperpolarized, nuclear magnetic resonance (NMR) to study hydrogenases under turnover conditions. So far undiscovered hydrogen species of the catalytic cycle of [Fe]-hydrogenases, are revealed and thus, extend the knowledge regarding this class of enzymes. These findings pave new pathways for the exploration of novel hydrogen metabolisms in vivo . We furthermore envision that the results contribute to the rational design of future catalysts to solve energy challenges of our society.