Our work corroborates the findings of Middleton and coworkers that amylin 20-29 forms both parallel and antiparallel β-sheet fibril polymorphs. Furthermore, the structures that we determine for both polymorphs exhibit hydrophobic zippers between the side chains of Leu, Ala, and Ile that are consistent with ssNMR data obtained by both the Middleton and Nielsen groups . In addition, the β-sheets of both polymorphs also exhibit a slight twist around their fibril axes, in agreement with the antiparallel β-sheet structure reported by Nielsen and coworkers . This agreement between our structural models and those derived from ssNMR data highlight the utility and complementary nature of using Raman spectroscopy to quantitatively assess the molecular structures of different amyloid fibrils.