SPECTROSCOPIC INVESTIGATIONS OF SYNTHETIC BETA-AMYLOID PEPTIDES OF ALZHEIMERS-DISEASE

The chemical mechanism of binding between Congo red dye and amyloid proteins was investigated using infrared spectroscopy. Synthetic amyloid corresponding to the amino-acid residues 1 to 28 of Alzheimer's beta amyloid and insulin fibers prepared with the Burke and Rougvie method were used as substrates. Both peptides clearly demonstrate beta-pleated sheet conformations. The analysis shows that Congo red binds to amyloid proteins via interactions between the two negatively-charged sulfonic acid groups of Congo red and two positively charged amino acid residues of amyloid protein molecules. Evidence leads to the conclusion that the beta-pleated sheet conformation of the protein aids in orienting the dye molecules, thus favoring stabilisation and bonding.