Surfactant-induced conformational transition of amyloid β-peptide

Accumulating evidence suggests that Aβ1–42–membrane interactions may play an important role in the pathogenesis of Alzheimer’s disease. However, the mechanism of this structural transition remains unknown. In this work, we have shown that submicellar concentrations of sodium dodecyl sulfate (SDS) can provide a minimal platform for Aβ1–42 self-assembly. To further investigate the relation between Aβ1–42 structure and function, we analyzed peptide conformation and aggregation at various SDS concentrations using circular dichroism (CD), Fourier transform infrared spectroscopy, and gel electrophoresis. These aggregates, as observed via atomic force microscopy, appeared as globular particles in submicellar SDS with diameters of 35–60 nm. Upon sonication, these particles increased in disc diameter to 100 nm. Pyrene I3/I1 ratios and 1-anilinonaphthalene-8-sulfonic acid binding studies indicated that the peptide interior is more hydrophobic than the SDS micelle interior. We have also used Forster resonance energy transfer between N-terminal labeled pyrene and tyrosine (10) of Aβ1–42 in various SDS concentrations for conformational analysis. The results demonstrate that SDS at submicellar concentrations accelerates the formation of spherical aggregates, which act as niduses to form large spherical aggregates upon sonication.