Targeted Control of Kinetics of β-Amyloid Self-association by Surface Tension-modifying Peptides

Brain tissue from Alzheimer's patients contains extracellular senile plaques composed primarily of deposits of fibrillar aggregates of β-amyloid peptide. β-Amyloid aggregation is postulated to be a major factor in the onset of this neurodegenerative disease. Recently proposed is the hypothesis that oligomeric intermediates, rather than fully formed insoluble fibrils, are cytotoxic. Previously, we reported the discovery of peptides that accelerate β-amyloid aggregation yet inhibit toxicity in vitro, in support of this hypothesis. These peptides contain two domains: a recognition element designed to bind to β-amyloid and a disrupting element that alters β-amyloid aggregation kinetics. Here we show that the aggregation rate-enhancing activity of the disrupting element correlates strongly with its ability to increase surface tension of aqueous solutions. Using the Hofmeister series as a guide, we designed a novel peptide with terminal side-chain trimethylammonium groups in the disrupting domain. The derivatized peptide greatly increased solvent surface tension and accelerated β-amyloid aggregation kinetics by severalfold. Equivalent increases in surface tension in the absence of a recognition domain had no effect on β-amyloid aggregation. These results suggest a novel strategy for targeting localized changes in interfacial energy to specific proteins, as a way to selectively alter protein folding, stability, and aggregation.