About the author: William Weeks is a PhD candidate in Chemistry under direction of Dr. Lauren Buchanan. In this article, Will and Dr. Buchanan determine how N-terminal acetylation causes aggregates of a model amphiphilic peptide, KFE8, to shift from a flat to a twisted ribbon structure. By utilizing the high spectral resolution of two-dimensional infrared spectroscopy coupled with isotope labeling and transition dipole coupling calculations, they were able to determine that acetylated KFE8 contains two β-sheet stacking arrangements, differing by a two-residue register shift, while the unmodified peptide only contains one. The methods developed in this work promise to aid the rational design of protein biomaterials by revealing how small changes in sequence affect structure at both the molecular and supramolecular level.