Inhibition of amyloid Ab aggregation by high pressures or specific D-enantiomeric peptides

Pressure can shift the polymer-monomer equilibrium of A beta, increasing pressure first leads to a release of A beta-monomers, surprisingly at pressures higher than 180 MPa repolymerization is induced. By high pressure NMR spectroscopy, differences of partial molar volumes Delta V-0 and compressibility factors Delta beta' of polymerization were determined at different temperatures. The D-enantiomeric peptides RD2 and RD2D3 bind to monomeric A beta with affinities substantially higher than those determined for fibril formation. By reducing the A beta concentration below the critical concentration for polymerization they inhibit the formation of toxic oligomers. Chemical shift perturbation allows the identification of the binding sites. The D-peptides are candidates for drugs preventing Alzheimer's disease. We show that RD2D3 has a positive effect on the cognitive behaviour of transgenic (APPSwDI) mice prone to Alzheimer's disease. The heterodimer complexes have a smaller Stokes radius than A beta alone indicating the recognition of a more compact conformation of A beta identified by high pressure NMR before.