The Amide II mode gives rise to a band located in the 1500 -1600 cm -1 region. It consists of an out-of-phase combination of NH in-plane bending and CN stretching. The Amide II is typically strong in IR spectra, but weak in Raman spectra excited with visible wavelengths. Interestingly, Lee and coworkers suggest that the Amide II is enhanced in the Raman spectra of parallel β-sheet structures. As seen in Figure , the Amide II is suppressed in the spectrum of amylin 20-29 polymorph 1 (Figure ), but appears in the spectra of the other two fibril polymorphs (Figure ). This suggests that amylin 20-29 polymorph 2 and Aβ 25-35 fibrils consist of parallel β-sheet structures.