CHARACTERIZTION OF β-SHEET PEPTIDES AND THIOFLAVIN T (THT) INTERACTIONS

Thioflavin T (ThT) is widely used as a fluorescent dye in methods for monitoring amyloid formation. In several serious diseases such as Alzheimer, Parkinson and type II diabetes, specific proteins undergo denaturation while forming fibrilar structures namely, amyloids. ThT molecules adsorbed on β-sheet structures show higher fluorescence signal yet, the molecular basis of this process is still not fully resolved. In order to characterize the interactions between β-sheet peptides in general and ThT, we used a set of synthetic and designed amphiphilic β-sheet forming peptides, sharing a few common structural motifs that differ in their hydrophilic amino acid composition, hence in molecular charge. The peptides were self-assembled to form β-sheet secondary structures in monolayers at air-water interface. Peptide assemblies in aqueous solutions were also induced. Assembled structures were characterized by various techniques including IR measurements at interfaces, and circular dichroism in solutions. These measurements were correlated with ThT binding assay to elucidate the sensitivity of the latter to β-sheet structure. Overall, our measurements demonstrated significant effect of β-sheet peptides` charge on ThT intensities. These results present valuable reference data to ThT assays applied generally to protein and peptide secondary structural characterizations and to detection of disease related amyloids.