Two different fibril polymorphs were prepared from the amylin 20-29 peptide using a modified procedure based on that developed by Madine et al. For both polymorphs, 2 mg of peptide were first disaggregated in 20 µL of DMSO after incubation at room temperature (22 °C) for 1 h. To prepare the antiparallel β-sheet polymorph (polymorph 1), 980 µL of water was slowly added, followed by an additional 1 mL of sodium phosphate buffer (20 mM, pH 7.13). The final solution was 2 mL with a final DMSO concentration of 1.41 × 10 -4 mM, 10 mM of buffer, and a peptide concentration of 1.13 mM. To prepare the parallel β-sheet polymorph (polymorph 2), 1980 µL of sodium phosphate buffer (100 mM, pH 7.13) was slowly added to the sample. The final solution was 2 mL with a final DMSO concentration of 1.41 × 10 -4 mM, 100 mM of buffer, and a peptide concentration of 1.01 mM. The final step for both polymorphs involved filtering solutions using a 0.45 µm pore-sized filter to remove any undissolved large aggregates. All starting solutions were visually clear and both samples were incubated at room temperature (22 °C). Aggregates could be visually observed after 7 days of incubation for polymorph 1 and 9 days for polymorph 2.