The distinct conformational dependence of chemical shifts caused by R-helices and β-sheets renders NMR chemical shift analysis a powerful tool for the structural determination of proteins. However, the time scale of NMR experiments can make a secondary structure assignment of highly flexible peptides or proteins, which may be converting between conformational substates, problematic. For instance the amyloid-β monomer, according to NMR chemical shifts, adopts a predominately random coil struc- ture in aqueous solution (with