We chose to study fibrils prepared from the amylin 20-29 and Aβ 25-35 peptides because of their small, tractable nature, which makes them ideal for quantitatively analyzing Ra- man spectra without the need for complex isotopic labeling schemes and performing detailed MD simulations. Studies suggest that residues 20 -29 form the amyloidogenic core of amylin. Fibrils prepared from amylin 20-29 can be poised to adopt well-defined morphologies, but there have been conflicting reports on whether it forms parallel, antiparallel, or mixed β-sheet fibril structures. Wildtype Aβ consists of two predominate isoforms, the 40-residue Aβ 1-40 and the 42-residue Aβ 1-42 . Although it is a less abundant isoform, Aβ 25-35 has also been found in the brain and has been shown to aggregate into β-sheet structures. Despite this, we are unaware of any known structures reported for Aβ 25-35 fibrils.