Quasielastic light scattering study of amyloid β-protein fibrillogenesis.

Quasielastic light scattering (QLS) spectroscopy is a noninvasive optical method for studying the dynamic properties of macromolecular solutions. Its most important application is the determination of diffusion coefficients, from which the sizes of particles in solution may be estimated. The technique thus is particularly useful for monitoring assembly (polymerization and aggregation) reactions without the need for removing aliquots from the assembly system or disrupting the assembly process in any other way. We discuss here two of the most important aspects of QLS: (1) measurement of the correlation function of the scattered light intensity and (2) the use of this correlation function to reconstruct the distribution of sizes of the scattering particles. The ability to monitor the temporal evolution of particle size provides a powerful tool for studying protein assembly. We illustrate here how QLS has been applied to elucidate features of the oligomerization and fibrillogenesis of the amyloid β-protein, Aβ, thought to be the causative agent of Alzheimer's disease.