Takayasu Kawasaki

Application of mid-infrared free-electron laser tuned to amide bands for dissociation of aggregate structure of protein

A mid-infrared free-electron laser (FEL) is a linearly polarized, high-peak powered pulse laser with tunable wavelength within the mid-infrared absorption region. It was recently found that pathogenic amyloid fibrils could be partially dissociated to the monomer form by the irradiation of the FEL targeting the amide I band (C=O stretching vibration), amide II band (N-H bending vibration) and amide III band (C-N stretching vibration). In this study, the irradiation effect of the FEL on keratin aggregate was tested as another model to demonstrate an applicability of the FEL for dissociation of protein aggregates. Synchrotron radiation infrared microscopy analysis showed that the α-helix content in the aggregate structure decreased to almost the same level as that in the monomer state after FEL irradiation tuned to 6.06 µm (amide I band). Both irradiations at 6.51 µm (amide II band) and 8.06 µm (amide III band) also decreased the content of the aggregate but to a lesser extent than for the irradiation at the amide I band. On the contrary, the irradiation tuned to 5.6 µm (non-absorbance region) changed little the secondary structure of the aggregate. Scanning-electron microscopy observation at the submicrometer order showed that the angular solid of the aggregate was converted to non-ordered fragments by the irradiation at each amide band, while the aggregate was hardly deformed by the irradiation at 5.6 µm. These results demonstrate that the amide-specific irradiation by the FEL was effective for dissociation of the protein aggregate to the monomer form.

Perivascular Accumulation of β-Sheet-Rich Proteins in Offspring Brain following Maternal Exposure to Carbon Black Nanoparticles

Environmental stimulation during brain development is an important risk factor for the development of neurodegenerative disease. Clinical evidence indicates that prenatal exposure to particulate air pollutants leads to diffuse damage to the neurovascular unit in the developing brain and accelerates neurodegeneration. Maternal exposure to carbon black nanoparticles (CB-NPs), used as a model for particulate air pollution, induces long-lasting diffuse perivascular abnormalities. We aimed to comprehensively characterize the perivascular abnormalities related to maternal NPs exposure using Fourier transform infrared microspectroscopy (in situ FT-IR) and classical staining analysis. Pregnant ICR mice were intranasally treated with a CB-NPs suspension (95 μg/kg at a time) on gestational days 5 and 9. Brains were collected 6 weeks after birth and sliced to prepare 10-μm-thick serial sections. Reflective spectra of in situ FT-IR were acquired using lattice measurements (x-axis: 7, y-axis: 7, 30-μm apertures) around a centered blood vessel. We also performed mapping analysis of protein secondary structures. Serial sections were stained with using periodic acid-Schiff or immunofluorescence to examine the phenotypes of the perivascular areas. Peaks of amide I bands in spectra from perivascular areas were shifted by maternal NPs exposure. However, there were two types of peak-shift in one mouse in the exposure group. Some vessels had a large peak-shift and others had a small peak-shift. In situ FT-IR combined with traditional staining revealed that the large peak-shift was induced around blood vessel adjacent to astrocytes with glial fibrillary acidic protein and aquaporin-4 over-expression and perivascular macrophages (PVMs) with enlarged lysosome granules. Furthermore, protein secondary structural analysis indicated that maternal NPs exposure led to increases in β-sheet content and decreases in α-helix content in areas that are mostly close to the centered blood vessel displaying histopathological changes. These results suggest that β-sheet-rich waste proteins, which are denatured by maternal NPs exposure, likely accumulate in the perivascular space as they are processed by the clearance systems in the brain. This may in turn lead the denaturation of PVMs and astrocyte activation. The risk of neurodegeneration may be enhanced by exposure to particulate air pollutants during brain development following the perivascular accumulation of β-sheet-rich waste proteins.

Restoration from polyglutamine toxicity after free electron laser irradiation of neuron-like cells

Proteins containing an expanded polyglutamine tract tend to aggregate, leading to the neuronal damage observed in polyglutamine diseases. We recently reported that free electron laser (FEL) irradiation markedly dissociates naked polyglutamine aggregates as well as the aggregate in the 293 T cells. In the present study, we investigated whether FEL irradiation of neuron-like cells with polyglutamine aggregates would restore the cellular damage and dysfunction. The aggregated polyglutamine peptides induced neurite retraction of differentiated SH-SY5Y cells. Upon FEL irradiation, the polyglutamine aggregates in the SH-SY5Y cells were dissociated, and the shorter length of individual neurite, fewer number of neurites per cell and shorter total length of neurite by polyglutamine were inhibited. Same results were essentially obtained in PC12 cells. Moreover, when FEL irradiation was applied to undifferentiated SH-SY5Y cells, the deficits in neuron-like differentiation seen in expanded polyglutamine peptide-containing cells were also rescued. Thus, FEL irradiation restored both the damage and differentiation caused by polyglutamine in neuron-like cells.

Breaking down cellulose fibrils with a mid-infrared laser

AbstractA novel process for the separation of crystalline cellulose in water into single polysaccharide strands is proposed that does not require high temperatures or other chemical reactants. We have modeled the behavior of a 36-strand cellulose

Resist-polymer ablation by mid-infrared-free-electron laser

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Erratum to: Picosecond pulsed infrared laser tuned to amide I band dissociates polyglutamine fibrils in cells.

Iβ crystalline bundle when subjected to picosecond mid-infrared laser pulses using all-atom non-equilibrium molecular dynamics simulations. We show that mid-infrared laser pulses that induce resonance deformations in the C–O–H angles of the hydroxyl groups that are involved in the hydrogen bonding network of cellulose, rapidly cause the cellulose bundles to dissociate into single strands solvated by the water. The laser pulses selectively disrupt intra- and inter-chain hydrogen bonds that maintain the polysaccharide strands in sheets and bundles, causing cellulose to dissolve into single strands whose end-to-end lengths remain similar to those in the original cellulose crystalline bundle. This proof-of-concept work provides guidance for experiments that may provide insight into the mechanism of cellulase enzymes whose improvement could lead to increased production of ethanol from cellulose, and possibly spur the development of new nanomaterial engineering techniques.Graphical Abstract

Effect of Mid-infrared Free-Electron Laser Irradiation on Refolding of Amyloid-Like Fibrils of Lysozyme into Native Form

We characterized the reactivity of a model metal resist for extreme ultraviolet (EUV) lithography by using a midInfrared free electron laser (mid-IR FEL). The evaluated metal resist consisted of a zirconium-oxide core and methacrylic-acid (MAA) ligands. The mid-IR spectra of the metal resist were measured to study photoresponse to FEL irradiation. In the spectra, the metal resist exposed with EUV light showed decreases of peaks of MAAs coordinating a metal core and new peaks have emerged. Mid-IR FEL study suggested that the EUV exposure made ligands of the metal resist more reactive, which are possible pointers increasing the sensitivity of the metal resist.

Mid-infrared free-electron laser tuned to the amide I band for converting insoluble amyloid-like protein fibrils into the soluble monomeric form

Laser ablation of poly(4-hydroxystyrene) (PHOST) film was studied using mid-Infrared free-electron laser (mid-IR FEL), of which irradiation wavelength was tuned to the vibrational absorption peaks of PHOST in mid-IR spectral region. A PHOST film was ablated by mid-IR FEL light to produce a clear hole in a PHOST film which suggested the photochemical ablation. As the threshold energy for silicon ablation was larger than that of PHOST, it was possible to ablate a PHOST film without any damage to a silicon substrate. The ablation threshold-energy ratio for PHOST to silicon was less than 0.2 and depended on the mid-FEL wavelength. The ablation threshold for a PHOST film depended also on the film thickness. The highly efficient ablation by mid-IR FEL was found to be due to the vibrational excitations of C-O stretching and C-O-H bending of PHOST.