A kinetic study on the aggregation behavior of £]-amyloid peptides in different initial solvent environments

Abstract

£]-Amyloid peptide (A£]) is the major proteinacious constituent of senile plaques in Alzheimer's disease and is believed to be responsible for the neurodegeneration associated with the disease. This work is aimed at determining the effect of solvent environment on the aggregation kinetics of A£] peptides. Prior to dilution into phosphate buffer saline, we have used three different initial solvent systems, 0.1% (v/v) trifluoroacetic acid in deionized water, 100% (v/v) dimethylsulfoxide, and 8 M urea to solubilize A£] peptides. Our research shows that the increase in ThT fluorescence intensity or absorbance elicited by aggregated species of A£] peptides exhibited a solvent environment-dependent behavior. Results from A£] aggregation in trifluoroacetic acid-phosphate buffer saline and dimethylsulfoxide-phosphate buffer saline systems suggested the involvement of the seeding effect. Moreover, with the aid of three proposed reaction schemes, the effect of this solvent environment-dependent behavior was quantitatively analyzed. We believe that a better understanding of how A£] species and its derivatives aggregate/self-assemble will shed light on the design and analysis of future work in this area. ? 2005 Elsevier B.V. All rights reserved.