<div>We combine absorption and fluorscence spectroscopy experiments and theoretical modeling to specifically examine the role of termini interactions on the optical properties.</div><div><div>Optical absorption and fluorescence is measured for a six-chain amino acid 2Y3J (AIIGLM) which forms a segment of the full amyloid beta 1-40. In order to explore the sensitivity of the optical properties to the termini interactions, the experiments were repeated by acetylating the N-terminus.</div><div>Although atomic force microscopy experiments indicate the formation of some form of fibrilar or crystal aggregates in both systems, the optical properties are strikingly different - acetylation significantly reduces optical activity between 280-350 nm.</div></div>

<div>We combine absorption and fluorscence spectroscopy experiments and theoretical modeling to specifically examine the role of termini interactions on the optical properties.</div><div><div>Optical absorption and fluorescence is measured for a six-chain amino acid 2Y3J (AIIGLM) which forms a segment of the full amyloid beta 1-40. In order to explore the sensitivity of the optical properties to the termini interactions, the experiments were repeated by acetylating the N-terminus.</div><div>Although atomic force microscopy experiments indicate the formation of some form of fibrilar or crystal aggregates in both systems, the optical properties are strikingly different - acetylation significantly reduces optical activity between 280-350 nm.</div></div>