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Biochem J. 2009 Jul 15;421(3):415-23. doi: 10.1042/BJ20090379.

Antiparallel beta-sheet: a signature structure of the oligomeric amyloid beta-peptide.

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  • 1Center for Structural Biology and Bioinformatics, Laboratory for Structure and Function of Biological Membranes, FacultĂ© des Sciences, UniversitĂ© Libre de Bruxelles, CP 206/2, Blvd. du Triomphe, B-1050 Brussels, Belgium.


AD (Alzheimer's disease) is linked to Abeta (amyloid beta-peptide) misfolding. Studies demonstrate that the level of soluble Abeta oligomeric forms correlates better with the progression of the disease than the level of fibrillar forms. Conformation-dependent antibodies have been developed to detect either Abeta oligomers or fibrils, suggesting that structural differences between these forms of Abeta exist. Using conditions which yield well-defined Abeta-(1-42) oligomers or fibrils, we studied the secondary structure of these species by ATR (attenuated total reflection)-FTIR (Fourier-transform infrared) spectroscopy. Whereas fibrillar Abeta was organized in a parallel beta-sheet conformation, oligomeric Abeta displayed distinct spectral features, which were attributed to an antiparallel beta-sheet structure. We also noted striking similarities between Abeta oligomers spectra and those of bacterial outer membrane porins. We discuss our results in terms of a possible organization of the antiparallel beta-sheets in Abeta oligomers, which may be related to reported effects of these highly toxic species in the amyloid pathogenesis associated with AD.

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