Structure of the β-Amyloid₍₁₀_-₃₅₎ Fibril

Abstract

The primary component of the amyloid plaques in Alzheimer's disease (AD) is a highly ordered fibril composed of the 39−43 amino acid peptide, β-amyloid (Aβ). The presence of this fibril has been correlated with both the onset and severity of the disease. Using a combination of synthetic model peptides, solid-state NMR, electron microscopy, and small angle neutron scattering (SANS), methods that allowed fibrils to be studied directly both in solution and in the solid state, the three-dimensional structure of fibrils formed from Aβ(10-35) is assigned. The structure consists of six laminated β-sheets propagating and twisting along the fibril axis. Each peptide strand is oriented perpendicular to the helical axis in a parallel β-sheet, with each like amino acid residue in register along the sheet. The six sheets are laminated, probably also in parallel arrays, to give a fibril with dimensions of about 60 × 80 Å. Both the methodology developed and the structural insight gained here lay the foundation for strategies to characterize and design materials capable of amyloid-like self-assembly.