1. Medical Scientist Training Program, Washington University School of Medicine 1 , Saint Louis, Missouri 63110, USA
2. Department of Physics, Washington University in St. Louis 2 , Saint Louis, Missouri 63130, USA
3. Department of Chemistry, Washington University in St. Louis 3 , Saint Louis, Missouri 63130, USA
4. Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine 4 , Saint Louis, Missouri 63110, USA