Raman optical activity of amyloid fibrils : a distinctive chiroptical phenomenon beyond resonance

Raman optical activity (ROA) exhibits dual characteristics for analysis of biological systems. Despite its excellent stereosensitivity and ability to study samples in aqueous solutions, the weak ROA signals limit its applicability in the case of biological samples, for which analyte concentrations are typically low. Therefore, there is considerable interest in developing techniques to enhance ROA signals. Most of the proposed approaches, which we review here, exploit a certain form of resonance. Against this background, we discuss a newly observed phenomenon, namely, the exceptionally intense ROA signals of amyloid fibrils, focusing on the nature of this effect, future works necessary to confirm its origin and its potential utility in the analysis of amyloid fibrils.