Conformational change of a synthetic amyloid analogue des[Ala21,30]A42 upon binding to octyl glucoside micelles.

The secondary structure of a synthetic amyloid fragment des [Ala21,30]A42 was studied by circular dichroism and Fourier transformed infrared spectroscopy. Measurements were performed in trifluoroethanol/water and octyl beta-D-glucopyranoside solutions. The spectra of the peptide in trifluoroethanol indicate a high percentage of alpha-helical structure. However, in octyl glucoside, at and above the critical micelle concentration, the peptide adopts a beta-sheet conformation. Secondary structure analysis yields a predominant (> 70%) beta-sheet content. Our data suggest that the peptide backbone or polar side groups of des[Ala21,30]A42 interact with the sugar-coated surface of micelles, which promotes an alpha to beta conformational transition.