[1] Univ Penn, Ctr Mol Modeling, Dept Chem, Philadelphia, PA 19104 USA
[2] Univ Penn, Biophys Engn Lab, Dept Chem & Biomol Engn, Philadelphia, PA 19104 USA
[3] Univ Penn, Lab Res Struct Matter, Philadelphia, PA 19104 USA
[4] Max Planck Inst Colloids & Interfaces Golm, D-14424 Potsdam, Germany