Two molecules that occur naturally in blood have been engineered by scientists from the UK and Japan to use sunlight to split water into hydrogen and oxygen. The discovery could provide an alternative and environmentally viable way to power a future hydrogen economy in which fossil fuels are largely replaced by renewables and hydrogen becomes the raw fuel stock.

Eishun Tsuchida and from Waseda University, Japan, working with Stephen Curry's team at Imperial College London, have synthesized a complex of the protein albumin, which is found at high levels in blood serum, and porphyrin, the molecular core of hemoglobin, which transports oxygen molecules around the body. The team switched the porphyrin's natural iron centre for zinc to change its chemistry entirely.

By combining the modified porphyrin with a genetically engineered albumin, the team could make a light sensitive molecular complex. This compound can trap energy from sunlight in such a way that allows the molecule to then split water molecules into their component hydrogen and oxygen.

Structural biologist Curry, explains the process: "This work has shown that it is possible to manipulate molecules and proteins that occur naturally in the human body by changing one small detail of their make-up, such as the type of metal at the heart of a porphyrin molecule, as we did in this study. It's very exciting to prove that we can use these biological structures as a conduit to harness solar energy to separate water out into hydrogen and oxygen."

In the long term, synthetic molecules and their chemical cousins may provide a more environmentally friendly way of producing hydrogen, which can be used as a 'green' fuel.

http://www.bio.ph.ic.ac.uk/~scurry/