1. Center for Nanotechnology in Drug Delivery and Division of Pharmacoengineering and Molecular Pharmacuetics Eshelman School of Pharmacy University of North Carolina at Chapel Hill Chapel Hill NC 27599 USA
2. Biochemistry and Biophysics University of North Carolina at Chapel Hill Chapel Hill NC 27599 USA
3. Laboratory of Chemical Design of Bionanomaterials Faculty of Chemistry M.V. Lomonosov Moscow State University Moscow 119992 Russia