1. Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel
2. Forschungszentrum Karlsruhe GmbH, Institut für Synchrotronstrahlung, D-76344 Germany
3. Department of Biomaterials, Max-Planck Institute of Colloids and Interfaces, Potsdam D-14424 Germany
4. Department of Chemical Engineering, University of California, Santa Barbara, California 93106
5. Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521