Development of a novel diffusion-based method to estimate the size of the aggregated A£] species responsible for neurotoxicity

Abstract

£]-Amyloid peptide (A£]) is the primary protein component of senile plaques in Alzheimer's disease and is believed to be responsible for the neurodegeneration associated with the disease. A£] is toxic only when aggregated, however, the size and structure of the aggregated species associated with toxicity is unknown. In the present study, we developed a diffusion-based method to simultaneously separate and detect the biological activity of toxic A£] oligomers and used the method to examine the relationship between size of aggregated protein and toxicity to SH-SY5Y cells. From these measurements, the effective diffusivity and hydrodynamic radius of the toxic oligomeric species of A£] could be determined. A sensitivity analysis was performed to examine the effects of model assumptions used in data analysis on the effective diffusivity calculated. The method provides a new estimate of the size of small toxic A£] species associated with fibril formation. This work contributes to our understanding of the relationship between A£] structure and toxicity and with further refinements may aid in our ability to design agents which alter the A£] aggregation/dissociation processes associated with neurotoxicity. ? 2002 Wiley Periodicals, Inc.