Elucidating the structure of the cross-beta core in large amyloid fibrils is a challenging problem in modern structural biology. For the first time, a set of de novo polypeptides was genetically engineered to form amyloid-like fibrils with similar morphology and yet different strand length. Differential ultraviolet Raman spectroscopy allowed for separation of the spectroscopic signatures of the highly ordered P-sheet strands and turns of the fibril core. The relationship between Raman frequencies and Ramachandran dihedral angles of the polypeptide backbone indicates the nature of the P-sheet and turn structural elements.