1 Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany and Center for Nanoscience, Ludwig-Maximilians University, Munich, Germany. weck@biochem.mpg.de.
2 Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany and Center for Nanoscience, Ludwig-Maximilians University, Munich, Germany. heuer-jungemann@biochem.mpg.de.