Aug 12 2019
Amyloid fibrils, which are a kind of self-assembled proteins/peptides, adopt a stacked sheet-like configuration.
It has been identified that amyloid fibril aggregates cause many diseases—including Alzheimer’s—and thus, it is of great scientific interest to learn how these aggregates can be broken. Furthermore, certain kinds of amyloid fibrils play a role in regulating gene expression in some organisms.
It is also assumed that the fiber-like formats occurring in these aggregates serve as scaffolds on which the biomaterials are grown. Thus, an ideal method for breakdown or “dissociation” of amyloid protein fibrils is important from the viewpoint of medical treatment, modification of biological structures and functions, and even biomaterial engineering.
A collaborative team of Japanese researchers from the IR Free Electron Laser Research Center at Tokyo University of Science and The Institute of Scientific and Industrial Research at Osaka University, including Dr Takayasu Kawasaki, Prof Koichi Tsukiyama, and Asst Prof Akinori Irizawa, has now demonstrated that it is possible to use a far-infrared (FIR) free-electron laser (FEL), known as FIR-FEL, to decompose amyloid protein aggregates, which is an evidence for the power of interdisciplinary scientific study.
This research has been reported recently in Scientific Reports.
We wanted to demonstrate the applicability of strong free-electron lasers in the life sciences, and this interdisciplinary research has made this possible.
Dr Takayasu Kawasaki, IR Free Electron Laser Research Center, Tokyo University of Science
Earlier studies have examined the dissociation of amyloid fibrils but with restricted success and inconsistent results. As their dissociation in water is complicated, physical approaches of dissociation have been studied in the past.
Electromagnetic radiation and lasers have been used for fabrication and structural/functional change of biological and chemical materials. Among lasers, not much research has been done on the FIR-FEL, though it has high penetration power and is absorbed well by biological systems. In addition, it is employed in tissue imaging, biophysics studies, and cancer diagnostics.
Kawasaki describes, “Our study shows for the first time that FIR-FEL is also useful for breaking down the fibril aggregate structure of proteins.”
For their research, the scientists used the 5-residue peptide DFKNF as the model since the association between its fibrillation and pathogenesis is already known. This peptide assembles automatically into a fibril sheet.
They discovered that FIR-FEL damaged the rigid β-sheet conformation (one of the few structures adopted by proteins) of the 5-residue peptide by developing small holes on the peptide film. They also discovered that FIR-FEL also disturbs the hydrogen bonds between adjacent β-sheets in the fibril and results in free peptides. This is called dissociation.
After that, Kawasaki and group checked for conformational modifications in the peptide fibril following irradiation with FIR-FEL, by analyzing the ratios of four kinds of secondary structures of peptides (α-helix, β-sheet, β-turn, and other). They identified that the proportion of the β-sheet conformation was substantially decreased, which implies that the rigid sheet-like structure of the fibril was disordered.
Kawasaki reports that prior research had also found mid-infrared (MIR)-FEL to be effective in this aspect.
We compared the effects of MIR-FEL with those of FIR-FEL, and we found that although MIR-FEL caused conformational changes in the fibril aggregates, it did not break down the fibrils as effectively as FIR-FEL did.
Dr Takayasu Kawasaki, IR Free Electron Laser Research Center, Tokyo University of Science
The scientists used scanning electron microscopy and dye staining methods to prove that FIR-FEL leads to morphological variations in the fibrils. Kawasaki states, “Because amyloid fibril peptides are involved in regulation of biological functions as well as pathologies, physical modification techniques (like FIR-FEL) could also be used to alter the biological functions of these macromolecules as needed.”
Since FIR-FEL is more efficient than MIR-FEL, it can be used to destroy amyloid fibrils deep within tissues, as in the case of Alzheimer’s disease. On the other hand, MIR-FEL can be employed for eliminating dermal amyloids on the skin surface.
Additionally, since fibril proteins serve as scaffolds for biocompatible materials, FIR-FEL could be employed in biomaterial engineering in regenerative medicine or nano-carrier drug-delivery systems.
Kawasaki concludes by articulating, “For the first time in the world, we have found that a rigid aggregate of amyloid fibrils can be effectively broken down using a free-electron laser in the terahertz region (wavelength 50-100 micrometers). Our next step would be to understand how FIR-FEL affects different types of peptide fibrils.”
He continued, “Our research can fuel the development of novel treatments for intractable diseases such as Alzheimer’s. It could also aid the development of new methods for manipulating the structure of biocompatible materials.”