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 t
Contact: Susan Trulove