Spectroscopic detection of β -sheet structure in nascent Aβ oligomers

Deep-UV resonance Raman (UVRR) spectroscopy and circular dichroism (CD) were employed to study the secondary structure of Aβ(1-42) in fresh samples with increasing fractions of oligomeric peptide. A feature with a minimum at ~217 nm appeared in CD spectra of samples containing oligomeric Aβ(1-42). UVRR spectra more closely resembled those of disordered proteins. The primary difference between UVRR spectra was the ratio of the 1236 cm(-1) to 1260 cm(-1) amide III peak intensities, which shifted in favor of the 1236 cm(-1) band as the fraction of oligomeric peptide increased.