1. Division of Chemical Biology and Medicinal Chemistry, UNC Eshelman School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
2. Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
3. Interdisciplinary Nanotoxicity Center, Department of Chemistry, Physics and Atmospheric Sciences, Jackson State University, Jackson, MS 39217, USA.
4. Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.