Previous studies have investigated the dissociation of amyloid fibrils but with limited success and mixed results. Because their dissociation in water is difficult, physical methods of dissociation have been explored in the past. Lasers and electromagnetic radiation have been used for fabrication and structural/functional alteration of chemical and biological materials. Among lasers, the FIR-FEL has been studied very sparsely, although it has high penetration power and is absorbed well by biological systems. It is also used in tissue imaging, cancer diagnostics, and biophysics studies. Kawasaki explains, "Our study shows for the first time that FIR-FEL is also useful for breaking down the fibril aggregate structure of proteins."
For their study, the researchers used the 5-residue peptide DFKNF as the model because the link between its fibrillation and pathogenesis is already established. This peptide auto-assembles into a fibril sheet. They found that FIR-FEL damaged the rigid ?-sheet conformation (one of the few structures that proteins assume) of the 5-residue peptide by creating small holes on the peptide film. The researchers found that FIR-FEL also disrupts the hydrogen bonds between adjacent ?-sheets in the fibril and gives rise to free peptides. This is referred to as dissociation.
Kawasaki - Team - Changes - Peptide - Fibril
Kawasaki and team then checked for conformational changes in the peptide fibril after irradiation with FIR-FEL, by analyzing the ratios of 4 types of secondary structures of peptides (?-helix, ?-sheet, ?-turn, and other). They found that the proportion of the ?-sheet conformation was drastically reduced, which suggests that the rigid sheet-like structure of the fibril was disrupted.
Kawasaki states that...
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