Temperature dependence of the nucleation constant rate in β amyloid fibrillogenesis

β-Amyloid peptide (Aβ), in fibrillar form, is the primary constituent of senile plaques, a defining feature of Alzheimer's disease (AD). In solution assays, fibrils form with a lag time, interpreted as a nucleation/condensation-dependent process. The kinetics of fibrillogenesis is controlled by two key parameters: nucleation and elongation rate constants. We report here the study of the temperature dependence of the nucleation rate constant on an Aβ monomer concentration of 18.4 μM at pH 7.4 and at temperatures ranging from 302 to 318 K. We found that the nucleation constant varied as in the Arrhenius law, giving an activation energy of 311.2 kJ mol−1. The corresponding values of enthalpy of activation (ΔH*), entropy of activation (ΔS*) and Gibbs energy of activation (ΔG*) were evaluated by Eyring's equation of absolute reaction rate. A Gibbs energy of activation of ∼110 kJ mol−1 was obtained.