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Alex Johs: Using neutrons for biological and environmental science

Alex Johs studies the molecular interactions that drive mercury transformation in the environment. Photographed by Genevieve Martin, ORNL.

Topic: Clean Energy

Sometimes solutions to the biggest problems can be found in the smallest details. The work of biochemist Alex Johs at Oak Ridge National Laboratory bears this out, as he focuses on understanding protein structures and molecular interactions to resolve complex global problems like the spread of mercury pollution in waterways and the food supply.

A puzzle-solver by nature, Johs works at the intersection of biology, chemistry, and physics. He uses neutrons to ‘see’ the molecular workings of microbes that transform benign forms of mercury into toxic methylmercury as well as microbes that remove the toxin from the environment. Johs takes those fundamental discoveries and applies them to developing technologies for mercury remediation.

“It is quite challenging,” Johs said. “Once a contaminant has spread in the environment, it is really hard to get it back out.”

Alex Johs uses the Bio-SANS instrument at ORNL’s High Flux Isotope Reactor in his biological and environmental research. Photographed by Carlos Jones, ORNL.

A penchant for problem-solving
Insights into the mechanics of how mercury transforms in the environment are essential to developing new solutions to address this worldwide environmental health issue. The fact that methylmercury “affects all of us” is what drives and inspires Johs’s research, he says.

Early in his career at ORNL, Johs was part of a cross-disciplinary team that solved a critical piece of the longstanding mystery surrounding how bacteria transform mercury into a highly toxic form. Using chemistry combined with analysis of genomic sequencing data, the team identified the pair of genes that code for two proteins, which enable the addition of a methyl group to mercury.

Since then, Johs and colleagues have focused on learning more about the biochemistry of the protein, combining laboratory experiments and modeling to predict the placement of its atoms. These mechanistic discoveries are vital to understanding how the protein methylates mercury—and potentially how to disrupt that process.

Mercury resistance is another focus for Johs. Some microorganisms can live in areas with high levels of mercury. The ways they survive and remove mercury from the environment are of extreme interest to Johs and colleagues. 

Neutron scattering has been key to gaining new knowledge about the molecular mechanisms at play without destroying the fragile proteins or cell components under study. 

“Neutrons bring a lot of advantages to these studies like the ability to vary the contrast of the sample,” Johs said. Gradually replacing hydrogen with deuterium allows the neutrons to highlight certain components while hiding others in the system under study. “This can be tremendously helpful.” 

Shining light with neutrons

It was ORNL’s world-class neutron sources that drew Johs to the laboratory. He had experienced how powerful a tool neutrons could be while working on his doctorate in biophysics at the Austrian Academy of Sciences, where he studied the structure of apolipoprotein B100, a central component in low density lipoprotein, often called ‘bad cholesterol.’ 

Previous attempts by others had yielded partial views of the protein, but the full structure remained elusive. Fresh from a six-week program called HERCULES or Higher European Research Course for Users of Large Experimental Systems at a neutron facility in Grenoble, France, Johs applied neutron science to reveal the protein structure.

That success spurred Johs to seek more opportunities to use neutrons for structural biology. He joined ORNL in 2007 as a postdoctoral researcher and used neutron reflectometry to examine protein interactions of iron-reducing bacteria that “breathe rocks” underground, gaining new insights into their respiration mechanisms. 

Johs became an ORNL staff member in early 2010 and has focused primarily on mercury science ever since. One of his current projects applies his molecular chemistry skills to evaluating and developing sorbent technologies that remove mercury from the environment. The ORNL team tests a range of commercial products and natural options like biochar. They aim to develop technologies that both absorb the toxin and prevent the erosion of mercury-containing riverbanks into waterways. Nearby East Fork Poplar Creek, which contains legacy mercury contamination, acts as their living laboratory.

When he fell in love with chemistry as a high schooler in Austria, Johs never imagined he would be working on such a broad range of research. He has collaborated with materials scientists and advanced manufacturing experts on bioderived precursors for carbon fiber as well.

“That is what’s really neat about ORNL,” Johs said. “You can collaborate with people who have different expertise and perspectives and get some really innovative solutions to challenging problems.”

In his personal time, Johs and his wife like to hike in national parks. Yellowstone and Yosemite are favorites, with the Great Smoky Mountains being a frequent weekend destination.

UT-Battelle manages ORNL for DOE’s Office of Science. The single largest supporter of basic research in the physical sciences in the United States, the Office of Science is working to address some of the most pressing challenges of our time. For more information, please visit