Analytical Sciences

Structural Discrimination between Aβ(1–40) and Aβ(1–42) Peptides in Films with Vibrational Circular Dichroism Spectroscopy

Toshinori MORISAKU and Hiroharu YUI

Department of Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku, Tokyo 162-8601, Japan

The secondary structure of full-length Aβ(1–40) and Aβ(1–42) peptides in films has been investigated with IR and vibrational circular dichroism (VCD) spectroscopy. From IR spectra, it is shown that the prepared films of Aβ(1–40) and Aβ(1–42) mainly comprise the β-sheet conformation that is characteristic of aggregated and fibrous Aβ. In the VCD spectra, the Aβ(1–42) film shows an intense and sharp band with left-handed optical activity at around 1625 cm⁻¹, while the Aβ(1–40) film shows a weak and broad band with right-handed activity at around 1630 cm⁻¹. The wavenumbers are characteristic of the β-sheet conformation. It has been clarified that the aggregated Aβ(1–42) adopts the β-sheet conformation with reverse optical activity compared with the aggregated Aβ(1–40). The left-handed optically active β-sheet of the aggregated Aβ(1–42) may contribute to the formation of protofibrils, which are a cause for the higher neurotoxicity of Aβ(1–42) fibrils than Aβ(1–40) fibrils.

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