Serena DeBeer of Cornell University and the Max Planck Institute for Bioinorganic Chemistry, led the the team that performed crucial experiments at SLAC. Dr. DeBeer is pictured above with Michael Roemelt and Frank Neese, also of the Max Planck Institute. Click here to see a photo of the nitrogenase enzyme.
We’re learning from plants every day – whether it’s by studying the process of photosynthesis to better learn how we can harness the power of the sun to generate electricity, or by studying algae's capacity to replace 17 percent of U.S. oil imports. Lessons learned from the Plant Kingdom have great potential to enable greater efficiency in America’s energy generation and industrial processes.
Why is this important? Well, for one thing, if we could make plant food from nitrogen the way nature does, we would have a much more efficient method for manufacturing fertilizer. The currently widespread industrial process of nitrogen fixation – the Haber-Bosch reaction – requires high temperatures and pressures, consuming 1.5 percent of the world’s energy. The fertilizer industry is a $17.8 billion industry in the United States alone.
An enzyme called nitrogenase plays a critical role in the natural process that soil microbes use to fix nitrogen, and for the past decade, researchers have been working to identify the key atom at the heart of nitrogenase.
“The fascination with this enzyme is the fact that it enables this reaction to take place at room temperature and atmospheric pressure,” said chemist Serena DeBeer of Cornell University and the Max Planck Institute for Bioinorganic Chemistry, who led the team that performed crucial experiments at SLAC. So hot was the race to identify the mystery atom that it ended in a photo finish: in the Nov. 18 issue of Science, two independent teams, using different approaches, identify the atom as carbon.
X-ray emission spectroscopy, or XES, which co-author Uwe Bergmann of SLAC (Read Energy.gov's 10 Questions with Dr. Bergmann) has developed over the past decade, was central to the team's research and identification of the mystery atom. The atom’s identity had eluded scientists because of its sequestered location inside a cluster of metal atoms.
SLAC scientists used an intense beam of X-rays from the Stanford Synchrotron Radiation Lightsource to knock the innermost electrons out of iron atoms in the cluster. Each time this happened, there was a tiny chance – less than one in a thousand – that the electron coming in to fill this hole would be from a neighboring atom, rather than from the iron atom itself. This caused subtle differences in the X-ray emissions from the cluster that identified the neighboring atom to be carbon.
“Because it’s sequestered in the middle of a bunch of metal atoms and you’ve got no way to get your hands on it, it’s a really hard problem,” said chemist Brian Hoffman of Northwestern University, who has investigated nitrogenase for 30 years but was not involved in these studies. “What the team has done would appear to be a classic case where new technology leads to new science.”
Thanks to the power of SLAC’s light source, researchers are able to tap the molecular-level intelligence of the Plant Kingdom to make discoveries that could potentially help make a billion-dollar industry more efficient.