New study looks at biological enzymes as a source of hydrogen fuel

Davis has conducted research from the University of Illinois and the University of California that has brought chemists one step closer to reconstructing nature's most efficient machinery for generating hydrogen gas. This new development could help pave the way for the hydrogen fuel industry to play a greater role in the global push for greener energy sources.

The researchers report their findings in the Proceedings of the National Academy of Sciences. At the moment, hydrogen gas is produced in a very complex industrial process that limits its attractiveness for the market for environmentally friendly fuels, according to the researchers. In response, scientists are looking for biologically synthesized hydrogen that is far more efficient than the current human-made process, said chemistry professor and co-author Thomas Rauchfuss.

Biological enzymes, so-called hydrogenases, are nature's machines for the production and combustion of hydrogen gas. There are two variants of these enzymes, iron-iron and nickel-iron - named after the elements responsible for the chemical reactions. The new study focuses on the iron-iron grade because it does the job faster, the researchers said.

The team entered the study with a general understanding of the chemical makeup of the active sites within the enzyme. They hypothesized that the sites were composed of 10 parts: four carbon monoxide molecules, two cyanide ions, two iron ions and two groups of a sulfur-containing amino acid called cysteine.

The team found that the enzyme's engine was rather two identical groups with five chemicals: two carbon monoxide molecules, a cyanide ion, an iron ion, and a cysteine ​​group. The groups form a firmly connected unit, and the two units together form a motor with a total of 10 parts.

But the laboratory analysis of the enzyme synthesized in the laboratory revealed a final surprise, said Rauchfuß. "Our recipe is incomplete. We now know that 11 bits are required to build the active site engine, not 10, and we are looking for that one last bit."

Team members are not sure what kind of applications this new understanding of the enzyme iron-iron hydrogenase will lead to. However, research could provide an assembly kit that will be useful for other catalyst design projects.

"The finding from this study is that it is one thing to imagine using the real enzyme to produce hydrogen gas, but it is far more powerful to understand your makeup well enough to reproduce it for use in the laboratory to be able to, "said Rauchfuss.

Researchers from the Oregon Health and Science University also contributed to this study.

The National Institutes of Health supported this study.

Journal Reference:

Guodong Rao, Scott A. Pattenaude, Katherine Alwan, Ninian J. Blackburn, R. David Britt, Thomas B. Rauchfuss. The binuclear cluster of [FeFe] hydrogenase is formed with sulfur donated by cysteine of an [Fe(Cys)(CO)2(CN)] organometallic precursor. Proceedings of the National Academy of Sciences, 2019; 116 (42): 20850 DOI: 10.1073/pnas.1913324116