1. Departments of Biochemistry and Physics, Center for Structural Biology, 5140 BIOSCI/MRB III, Vanderbilt University, Nashville, Tennessee 37232-8725, and Center for Insoluble Protein Structures (inSPIN) and Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, DK-8000 Aarhus C, Denmark