1. BMT-Biomolecular Therapeutics GmbH, Brunnerstrasse 59, A-1235 Vienna, Austria, Center for Ultrastructure Research and Ludwig Boltzmann-Institute for Molecular Nanotechnology, University of Natural Resources and Applied Life Sciences, A-1180 Vienna, Austria, and Vrije Universiteit Brussel, Vlaams Interuniversitair Instituut voor Biotechnologie, Pleinlaan 2, B-1050 Brussel, Belgium