The reduced low-frequency Raman spectra of the fibrils are shown in Figure . Reducing the spectra casts the Raman intensities in terms of the vibrational density of states. This makes the reduced intensities proportional to the Raman scattering cross sections of fundamental (ν 0 → ν 1 ) transitions. The spectra of Aβ 25-35 (Figure ) and amylin 20-29 (Figure ) fibrils display relatively well-resolved and narrow peaks similar to those observed in low-frequency spectra of crystals, while the spectra of fibrils prepared from Aβ 1-40 (Figure ) and full-length amylin (Figure ,f) are considerably broader. As summarized in Table , the spectra of all fibril samples share key features: intense bands between 60 -140 cm -1 , several peaks between 240 -420 cm -1 , and shoulder features around ∼ 15 -40 cm -1 .