Wigginton's research at PNNL is based in part on the discoveries of Rudolph Marcus, who received the Nobel in chemistry in 1992 for his contributions to the theory of electron transfer reactions in chemical systems. Wigginton is using the PNNL's scanning tunneling microscope (STM) to study proteins from a bacterium called Shewanella. The U.S. Department of Energy (DOE) is particularly interested in Shewanella because it immobilizes certain minerals in ground water, including radioactive and heavy metals. Shewanella attaches to minerals as an energy source -- transferring electrons in a process similar to the way in which humans breathe oxygen.
The proteins that Wigginton is studying are the MtrC and OmcA enzymes, which reside on the cell surface and appear to initiate the process, or respiration pathway, by transferring electrons from the bacteria to the metals, "like an electrical wire," Wigginton said.The STM allows him to view the proteins at the nanoscale. He places pure protein on a gold film. The STM introduces a current and produces images of the conductivity. Wigginton is looking at the energetics of electron movement through the protein to the mineral surface. "The proteins have a system of iron atoms that are so close together that electrons can essentially hop across the gaps," he said.
The research is part of a multimillion-dollar DOE project at PNNL. Wigginton, who has been working on a research project at PNNL for four months, is one of some 40 scientists who have been working on similar issues and are now integrating their findings. "The goals are to understand the fundamental reactions that dictate how these bacteria interact with minerals -- to understand part of our natural environment, and to see if the DOE can use these bacteria to clean up sites that have been contaminated with, for instance, uranium," said Wigginton. "It could potentially be a safe and cost effective means of environmental remediation. I am studying some of the underlying mechanisms of that process."
Wigginton looks forward to discussing the research with Nobel laureate Marcus. "I also want to talk to other laureates about how science fits into society and how they communicate their research to the public. It would also be interesting to see how they feel science influences policy, especially considering the present challenges of finding efficient alternative energy sources."
Wigginton received his undergraduate degree in geology from Michigan State University, where he participated in a study abroad program in the Amazon rain forest. He will present his research at the 232nd National Meeting of the American Chemical Society in San Francisco this fall and has submitted articles for publication. Highlights of his early work are available online at www.emsl.pnl.gov/new/highlights/200504/ complete with an STM image showing 5 nanometer proteins.
Since 1951, Nobel Laureates in chemistry, physics, and physiology/medicine have met annually in Lindau to have open and informal discussions with students and young researchers. This year's event will focus on chemistry. The DOE, which includes the national laboratories like PNNL, and the National Science Foundation are invited to bring groups of top young researchers to the 56th annual meeting to participate in discussions with the Nobel Laureates. Wigginton is among 60 U.S. Ph.D. students and 500 students from across the world who will participate June 24-30.