Kinetics of amyloid [beta] monomer-to-oligomer exchange by NMR relaxation

NMR relaxation measurements are used for addressing the kinetics of exchange between monomeric and large, polymorphic oligomeric species of amyloid [beta] (A[beta](1-40)). The increase in [super 15]N and [super 1][H.sub.N][R.sub.2] rates as a function of protein concentration is independent of nucleus and magnetic field and the fraction of peptide within the dark oligomeric state undergoing exchange with free monomer is calculated.