Institute for Protein Research, Osaka University and CREST, Japan Science and Technology Agency, Yamadaoka 3-2, Suita, Osaka 565-0871, Japan.
To understand the mechanism by which amyloid fibrils form, we have been making real-time observations of the growth of individual fibrils, using total internal fluorescence microscopy combined with an amyloid-specific fluorescence dye, thioflavin T (ThT). At neutral pH, irradiation at 442 nm with a laser beam to excite ThT inhibited the fibril growth of beta(2)-microglobulin (beta2-m), a major component of amyloid fibrils deposited in patients with dialysis-related amyloidosis. Examination with a 22-residue K3 fragment of beta2-m showed that the inhibition of fibril growth and moreover the destruction of preformed fibrils were coupled with the excitation of ThT. Several pieces of evidence suggest that the excited ThT transfers energy to ground state molecular oxygen, producing active oxygen, which causes various types of chemical modifications. The results imply a novel strategy for preventing the deposition of amyloid fibrils and for destroying preformed amyloid deposits.