Abstract
Fibrous peptides such as amyloid fibrils have various roles in biological system, e.g., as causal factor of serious amyloidosis in human and as functional regulator of cell formation in bacteria and eukaryotes. In addition, the fiber-type format is promising as biocompatible scaffold. Therefore, the dissolution method of peptide fibril is potentially useful at many scenes in medical and material fields: as reductive way of pathogenic amyloid, as modification technique of cell structure, and as fabrication tool of biomaterials. However, the fibril structure is generally difficult to be dissociated due to its rigid stacked conformation. Here, we propose a physical engineering technology using terahertz free electron laser (FEL) at far-infrared wavelengths from 70 to 80 μm. Infrared microscopy analysis of the irradiated fibril of calcitonin peptide as a model showed that β-sheet was decreased, and α-helix, turn, and others were increased, compared to those of the fibril before the FEL irradiation. Interestingly, the dissociative effect by the far-infrared laser was remarkable than that by the mid-infrared laser tuned to 6.1 μm that corresponds to amide I. In addition, simple heating at 363 K deformed the fibril state but increased the amount of β-sheet, which was contrast with the action by the FEL, and scanning-electron microscopy and Congo-red staining revealed that the fibril was collapsed power-dependently within a range from 25 to 900 mJ energies supplied with the FEL at 74 μm. It can be considered that irradiation of intense terahertz wave can dissociate fibrous conformation of peptide with little influence of thermal effect.
Highlights
Fibrous peptides such as amyloid fibrils have various roles in biological system, e.g., as causal factor of serious amyloidosis in human and as functional regulator of cell formation in bacteria and eukaryotes
MIR-free electron laser (FEL) was originally applied for dissociation of amyloid fibrils for the purpose of development of novel physical engineering technique for the disease therapy, and we found that the mid-infrared FEL (MIR-FEL) tuned to wavelengths 6.1–6.2 μm can dissociate the aggregate structure of amyloid peptide into the non-aggregate form[27]
We found that the far-infrared FEL (FIR-FEL) irradiation tuned to 70–80 μm changed the fibril state of a peptide more remarkably than the MIR-FEL, as shown in the conformational changes of peptide
Summary
Fibrous peptides such as amyloid fibrils have various roles in biological system, e.g., as causal factor of serious amyloidosis in human and as functional regulator of cell formation in bacteria and eukaryotes. The stacking structure is a common characteristic in almost kinds of amyloid fibrils even though the amino acid sequences are different Another remarkable feature of the peptide fibril is such a tough fiber-like format. Development of structural deformation method of the fibrous aggregate will be expected to lead to processing system of solid biomaterials, reduction of pathogenic amyloid, and regulation of biological function associated with peptide fibrils. There have been several successful applications of the far-infrared laser and terahertz spectroscopy to bio-imaging of tissues and low-invasive diagnostics of cancer in medical field[17,18], and to the molecular study of water in biological physics[19]. We show that FIR-FEL exhibits remarkable performance in dissociation of fibril structure of a peptide
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