1. Institute of Bioengineering (IBI) and Institute of Chemical Sciences and Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne CH 1015, Switzerland, Department of Chemistry, University of California, Berkeley and Division of Materials Science, Lawrence Berkeley National Laboratory, Berkeley California 94720, and Laboratoire d’Analyse Ultrastructurale, Bâtiment de Biologie, University of Lausanne, Lausanne CH 1015, Switzerland