In nature, biological nanomachines called hydrogenases catalyze hydrogen gas production. These enzymes are responsible for turning surplus energy in microorganisms into hydrogen gas (H₂), for example, as a fleeting by-product of photosynthesis or respiration. Hydrogenases release more than 10,000 molecules of H₂ per second, which is why there is so much interest in understanding the reaction principles behind the enzyme. “In the future, it will be possible to use design-hydrogenases for the production of H₂ as a climate-neutral fuel,” says biophysicist Dr. Sven Stripp of Freie Universität Berlin, the corresponding author of the study.

According to Dr. Stripp, the hydrogenase reaction is basically very simple: Two protons (H⁺) are converted into H₂ with the help of two electrons that act as molecular “glue.” This reaction takes place in the center of the hydrogenase, which is formed by an iron-sulfur molecule. “The path the electrons take to get to the center is well understood, as is the path that the H₂ uses to leave the enzyme,” Stripp explains. His research team, working together with scientists from Bochum and Linz, was able to observe the transfer of protons for the first time under experimental conditions. The Berlin biophysicists made use of a common natural phenomenon: the simultaneous movement of electrons and protons. In their lab, they added a special dye to a highly active hydrogenase. When exposed to a green light, the dye releases an electron into the enzyme. Through extensive research, they knew that the catalytic center of the enzyme bonds a proton when it receives an electron. Changes in the protein environment caused by protonation could then be traced using infrared spectroscopy.