Samples were prepared for Raman characterization as previously described. Aliquots (250 -500 µL) of fibril solutions were centrifuged for 1 h at 21300×g (Eppendorf Centrifuge 5425). The supernatants were removed and the pellets containing fibrils were then washed 2× with water to remove residual salt. Aliquots of sample were then spotted onto aluminum foil covered microscope slides and dried in a dust free environment prior to Raman measurements.