1. Department of Biological Sciences, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada, Institute of Chemical Sciences and Engineering, Laboratory of Protein Engineering, École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland, and Groningen Biomolecular Sciences and Biotechnology Institute & Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands