title: Temperature dependence of the nucleation constant rate in beta amyloid fibrillogenesis.
abstract: Beta-amyloid peptide (A beta), 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 A beta monomer concentration of 18.4 microM 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 (deltaH*), entropy of activation (deltaS*) and Gibbs energy of activation (deltaG*) were evaluated by Eyring's equation of absolute reaction rate. A Gibbs energy of activation of approximately 110 kJ mol(-1) was obtained.
authors.affiliation: Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, Avda. Joan XXIII s/n 08028-Barcelona, Catalonia, Spain.
authors.forename: Raimon
authors.initials: R
authors.lastname: Sabaté
authors.forename: Montserrat
authors.initials: M
authors.lastname: Gallardo
authors.forename: Joan
authors.initials: J
authors.lastname: Estelrich
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016229:Amyloid beta-Peptides / Q000737:chemistry*; D019277:Entropy; D006358:Hot Temperature; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010455:Peptides / Q000737:chemistry; D013053:Spectrophotometry; D013223:Statistics as Topic; D013696:Temperature; D013816:Thermodynamics; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D016229:Amyloid beta-Peptides; D010455:Peptides