1. Department of Biological Sciences, Marquette University, Milwaukee, Wisconsin 53201-1881, United States
2. BioTechnology Institute, University of Minnesota, St. Paul, Minnesota 55108-6106, United States
3. Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota 55108-6106, United States
4. Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201-1881, United States