1 Lehrstuhl für Angewandte Physik and Center for Nanoscience, Ludwig-Maximilians-Universität, 80799 Munich, Germany; Department of Chemistry, University of Basel, 4056 Basel, Switzerland; Department of Biosystems Science and Engineering, Eidgenössische Technische Hochschule (ETH Zurich), 4058 Basel, Switzerland. Electronic address: michael.nash@lmu.de.
2 The Hebrew University of Jerusalem, POB 12, Rehovot 76100, Israel. Electronic address: Shoseyov@agri.huji.ac.il.