Amyloid fibrils are widely recognized as a cause of serious amyloidosis such as Alzheimer’s disease. Although dissociation of amyloid fibril aggregates is expected to lead to a decrease in the toxicity of the fibrils...Amyloid fibrils are widely recognized as a cause of serious amyloidosis such as Alzheimer’s disease. Although dissociation of amyloid fibril aggregates is expected to lead to a decrease in the toxicity of the fibrils in cells, the fibril structure is robust under physiological conditions. We have irradiated amyloid fibrils with a free-electron laser (FEL) tuned to mid-infrared frequencies to induce dissociation of the aggregates into monomer forms. We have previously succeeded in dissociating fibril structures of a short peptide of the thyroid hormone by tuning the oscillation frequency to the amide I band, but the detailed structural changes of the peptide have not yet been determined at a high spatial resolution. Synchrotron-radiation infrared microscopy (SR-IRM) is a powerful tool for in situ analysis of minute structural changes of various materials, and in this study, the feasibility of SR-IRM for analyzing the microscopic conformational changes of amyloid fibrils after FEL irradiation was investigated. Reflection spectra of the amyloid fibril surface showed that the amide I peaks shifted to higher wave numbers after the FEL irradiation, indicating that the initial β-sheet-rich structure transformed into a mixture of non-ordered and turn-like peptide conformations. This result demonstrates that conformational changes of the fibril structure after the FEL irradiation can be observed at a high spatial resolution using SR-IRM analysis and the FEL irradiation system can be useful for dissociation of amyloid aggregates.展开更多
Amyloid fibrils are deposited in various tissues in the body, and are linked to the putative causes of serious diseases such as amyloidosis. Although the conditions of the disease would be expected to improve if the f...Amyloid fibrils are deposited in various tissues in the body, and are linked to the putative causes of serious diseases such as amyloidosis. Although the conditions of the disease would be expected to improve if the fibril structure could be destroyed, the aggregated structure is stable under physiological conditions. Recently, we found that the amyloid fibrils of lysozyme could be refolded into their active form by using a mid-infrared free-electron laser (MIR-FEL) tuned to the amide I band (corresponding to the C=O stretch vibration), with the MIR-FEL having specific oscillation characteristics of a picosecond pulse structure, a tunable wavelength within mid-infrared frequencies, and high photon density. In the study, we tested the usability of the FEL for dissociation of aggregates of pathological amyloid fibrils by using a short peptide of human thyroid hormone. The fibrils (after being placed on a glass slide) were irradiated using the FEL tuned to the amide I band (1644 cm?1), and those in situ were analyzed by Congo-Red assay, scanning-electron microscopy, and transmission-electron microscopy. All of the results obtained using these microscopic analyses indicated that the amyloid fibril formation was considerably decreased by FEL irradiation. Moreover, upon irradiation, a strong fibril peak at the amide I band in the infrared spectrum was transformed into a broad peak. These results imply that the β-sheet-rich structure of the amyloid fibrils changed into non-ordered or unspecified structures after the FEL irradiation. This FEL irradiation system, combined with various analytical methods, shows promise for the dissociation of amyloid aggregates.展开更多
文摘Amyloid fibrils are widely recognized as a cause of serious amyloidosis such as Alzheimer’s disease. Although dissociation of amyloid fibril aggregates is expected to lead to a decrease in the toxicity of the fibrils in cells, the fibril structure is robust under physiological conditions. We have irradiated amyloid fibrils with a free-electron laser (FEL) tuned to mid-infrared frequencies to induce dissociation of the aggregates into monomer forms. We have previously succeeded in dissociating fibril structures of a short peptide of the thyroid hormone by tuning the oscillation frequency to the amide I band, but the detailed structural changes of the peptide have not yet been determined at a high spatial resolution. Synchrotron-radiation infrared microscopy (SR-IRM) is a powerful tool for in situ analysis of minute structural changes of various materials, and in this study, the feasibility of SR-IRM for analyzing the microscopic conformational changes of amyloid fibrils after FEL irradiation was investigated. Reflection spectra of the amyloid fibril surface showed that the amide I peaks shifted to higher wave numbers after the FEL irradiation, indicating that the initial β-sheet-rich structure transformed into a mixture of non-ordered and turn-like peptide conformations. This result demonstrates that conformational changes of the fibril structure after the FEL irradiation can be observed at a high spatial resolution using SR-IRM analysis and the FEL irradiation system can be useful for dissociation of amyloid aggregates.
文摘Amyloid fibrils are deposited in various tissues in the body, and are linked to the putative causes of serious diseases such as amyloidosis. Although the conditions of the disease would be expected to improve if the fibril structure could be destroyed, the aggregated structure is stable under physiological conditions. Recently, we found that the amyloid fibrils of lysozyme could be refolded into their active form by using a mid-infrared free-electron laser (MIR-FEL) tuned to the amide I band (corresponding to the C=O stretch vibration), with the MIR-FEL having specific oscillation characteristics of a picosecond pulse structure, a tunable wavelength within mid-infrared frequencies, and high photon density. In the study, we tested the usability of the FEL for dissociation of aggregates of pathological amyloid fibrils by using a short peptide of human thyroid hormone. The fibrils (after being placed on a glass slide) were irradiated using the FEL tuned to the amide I band (1644 cm?1), and those in situ were analyzed by Congo-Red assay, scanning-electron microscopy, and transmission-electron microscopy. All of the results obtained using these microscopic analyses indicated that the amyloid fibril formation was considerably decreased by FEL irradiation. Moreover, upon irradiation, a strong fibril peak at the amide I band in the infrared spectrum was transformed into a broad peak. These results imply that the β-sheet-rich structure of the amyloid fibrils changed into non-ordered or unspecified structures after the FEL irradiation. This FEL irradiation system, combined with various analytical methods, shows promise for the dissociation of amyloid aggregates.
