UCLA

Fibrillogenesis of the amyloid beta-protein (Abeta) is believed to play a central role in the pathogenesis of Alzheimer's disease. Previous studies of the kinetics of Abeta fibrillogenesis showed that the rate of fibril elongation is proportional to the concentration of monomers. We report here the study of the temperature dependence of the Abeta fibril elongation rate constant, ke, in 0.1 M HCl. The rate of fibril elongation was measured at Abeta monomer concentrations ranging from 50 to 400 microM and at temperatures from 4 degreesC to 40 degreesC. Over this temperature range, ke increases by two orders of magnitude. The temperature dependence of ke follows the Arrhenius law, ke = A exp (-EA/kT). The preexponential factor A and the activation energy EA are approximately 6 x 10(18) liter/(mol.sec) and 23 kcal/mol, respectively. Such a high value of EA suggests that significant conformational changes are associated with the binding of Abeta monomers to fibril ends.