S1 Morphology and Persistence Length of Amyloid Fibrils are Correlated to Peptide Molecular Structure Corianne C. vandenAkker, 1 Maarten F.M. Engel, 1 Krassimir P. Velikov, 2 Mischa Bonn, 1,3 Gijsje H. Koenderink 1, * 1 FOM Institute AMOLF, Science Park 104, 1098 XG, Amsterdam, The Netherlands 2 Unilever R&D Vlaardingen, Olivier van Noortlaan 120, 3133 AT Vlaardingen, The Netherlands; Soft Condensed Matter, Debye Institute for Nanomaterials Science, Department of Physics and Astronomy, Utrecht University, Princetonplein 5, 3584 CC, Utrecht, The Netherlands 3 Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany Materials and Methods Bovine β-lactoglobulin (genetic variants A and B, Sigma, L0130) was dissolved in HCl solution (pH 2). To remove traces of electrolytes, the solution was extensively dialyzed (Slide-a- Lyzer, MWCO 10kDa, Thermo) against an HCl solution (pH 2). Insoluble protein was removed by filtration (0.1 m filter, Millipore). The final protein concentration was determined using UV spectrophotometry (Perkin Elmer, Lambda 35 UV/VIS Spectrometer) at a wavelength of 278 nm based on an extinction coefficient 1 of 16.8 mM -1 cm -1 . To obtain fibrils of the desired morphology, a range of conditions was tested. The β-lactoglobulin stock solution was diluted with HCl solution (pH 2) to a concentration between 3.0 and 7.5% (w/w). Samples in an eppendorf tube were heated in an oven at 80°C during a period varying between 2 and 96 hours, followed by quenching in ice water. Fibrils were separated from non-aggregated material by centrifuging the solution over centrifugal filters (MWCO 100kDa, Millipore) at 1000 g for 30 min. 2 The retentate containing the fibrils was diluted with HCl (pH 2) and centrifuged two additional times over the centrifugal filters to remove residual non-aggregated material. To quantify the extent of protein