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論文

Dynamical behavior of human $$alpha$$-synuclein studied by quasielastic neutron scattering

藤原 悟; 荒木 克哉*; 松尾 龍人; 八木 寿梓*; 山田 武*; 柴田 薫; 望月 秀樹*

PLOS ONE (Internet), 11(4), p.e0151447_1 - e0151447_17, 2016/04

 被引用回数:18 パーセンタイル:67.4(Multidisciplinary Sciences)

Filamentous aggregates (amyloid fibrils) of the protein $$alpha$$-synuclein ($$alpha$$-Syn) are related to the pathogenesis of Parkinson's disease. To understand the pathogenesis mechanism of this disease, the mechanism of the amyloid fibril formation of $$alpha$$-Syn must be elucidated. As a first step toward this ultimate goal, dynamical behavior of $$alpha$$-Syn in the monomeric and the fibril states was investigated using quasielastic neutron scattering (QENS). Analysis of the QENS spectra of solution samples of $$alpha$$-Syn shows that diffusive global motions are observed in the monomeric state but largely suppressed in the fibril state. However, the amplitude of the side chain motion is shown to be larger in the fibril state than in the monomeric state. This implies that significant solvent space exists within the fibrils, which is attributed to the $$alpha$$-Syn molecules within the fibrils having a distribution of conformations. The larger amplitude of the side chain motion in the fibril state than in the monomeric state implies that the fibril state is entropically favorable.

論文

陽電子消滅法を用いたFe-Cu合金の低温時効硬化の評価

山下 孝子*; 勝山 仁哉; 佐藤 馨*; 水野 正隆*; 荒木 秀樹*; 白井 泰治*

鉄と鋼, 97(11), p.558 - 565, 2011/11

 被引用回数:0 パーセンタイル:0.01(Metallurgy & Metallurgical Engineering)

Fe-Cu合金の硬さは熱時効に伴うCu析出物により増加することが知られている。以前にわれわれは、引張や冷間圧延により予歪導入された格子欠陥が、硬さが増加する時効温度を低下させ、Cu析出を促進させることを報告した。しかしながら、その機構は明らかにされていない。そこで本研究では、陽電子寿命法及び同時計数ドップラー幅広がり法により、冷間圧延後熱時効を施したFe-Cu合金における空孔,空孔複合体,転位等の格子欠陥の回復挙動及び、Cu原子の拡散挙動を分析した。その結果、冷間圧延により導入された空孔及び転位の熱時効による回復挙動について、空孔は300$$^{circ}$$Cで完全に回復する一方、転位は550$$^{circ}$$Cでも一部残ることがわかった。またCuクラスターは、空孔の回復とともに析出し始め、おもに空孔のシンクスとなる転位の周辺に析出することがわかった。

口頭

Pre-strain effect on Cu precipitation in Fe-Cu alloys studied by positron annihilation techniques

勝山 仁哉; 山野 裕子*; 山下 孝子*; 水野 正隆*; 荒木 秀樹*; 白井 泰治*

no journal, , 

圧力容器鋼の硬化や脆性に影響すると考えられるCu析出への予歪み効果について、陽電子寿命法,同時計数ドップラー幅拡がり(CDB)法及びビッカース硬さ測定により評価検討を行った。Fe-1.5mass%Cu合金に830$$^{circ}$$C、10分の溶体化処理を施し、その後冷間圧延により30%, 50%, 70%の予歪みを付加した試料を作製した。焼鈍温度200$$^{circ}$$C$$sim$$600$$^{circ}$$C(焼鈍時間15分)で等時焼鈍を行いつつ、室温下で陽電子寿命, CDB及びビッカース硬さを測定した。その結果、予歪みを付加すると転位がCu析出物の核生成サイトとなり、予歪付加直後からCu析出物により硬化することがわかった。その後の焼鈍過程では、予歪みにより導入された空孔クラスターが200$$^{circ}$$C近傍で移動・回復することによりCu原子が拡散し、Cu析出物が成長するため、合金はさらに硬化する。500$$^{circ}$$C以上の温度では熱平衡空孔が導入され、それらの移動により予歪を付加しない合金でも硬化することが明らかとなった。

口頭

Changes in the dynamics of human $$alpha$$-synuclein and its relation to propensity for amyloid fibril formation

藤原 悟; 荒木 克哉*; 松尾 龍人; 八木 寿梓*; 山田 武*; 柴田 薫; 望月 秀樹*

no journal, , 

A protein $$alpha$$-synuclein ($$alpha$$-Syn), which is involved with pathogenesis of a neuro-degenerative disorder, Parkinson's disease, forms amyloid fibrils. Propensity for amyloid fibril formation depends on environmental conditions such as pH. We employed neutron scattering to investigate the "dynamic" behavior of $$alpha$$-Syn at low and neutral pH, to investigate the relationship between the dynamics and propensity for amyloid fibril formation. We carried out the quasielastic neutron scattering experiments using a high energy resolution near-backscattering spectrometer, BL02 (DNA), at MLF/J-PARC, Japan. Analysis of the quasielasitc scattering spectra showed the increased flexibility of $$alpha$$-Syn at low pH. Since the increased flexibility is likely to arise from a wider distribution of conformational substates of $$alpha$$-Syn, the results obtained suggest an entropy-driven mechanism of the amyloid fibril formation.

口頭

Quasielastic neutron scattering study of human $$alpha$$-synuclein; Implication for propensity for amyloid fibril formation

藤原 悟; 荒木 克哉*; 松尾 龍人; 八木 寿梓*; 山田 武*; 柴田 薫; 望月 秀樹*

no journal, , 

A protein $$alpha$$-synuclein ($$alpha$$-Syn) forms amyloid fibrils. This abnormal protein aggregation is related to pathogenesis of a neuro-degenerative disorder, Parkinson's disease. Propensity for amyloid fibril formation depends on environmental conditions such as pH. We carried out quasielastic neutron scattering experiments to investigate the "dynamic" behavior of $$alpha$$-Syn to investigate the relationship between the dynamics and propensity for amyloid fibril formation. The measurements on the solution samples of $$alpha$$-Syn in different pH were carried out using a high energy resolution near-backscattering spectrometer, BL02 (DNA), at MLF/J-PARC, Japan. Differences in flexibility of the protein were detected between the different conditions. Since the difference in flexibility is likely to arise from different distributions of conformational substates of $$alpha$$-Syn, the results obtained suggest an entropy-driven mechanism of the amyloid fibril formation.

口頭

Changes in the dynamics of human $$alpha$$-synuclein detected by neutron scattering

藤原 悟; 荒木 克哉*; 松尾 龍人; 八木 寿梓*; 山田 武*; 柴田 薫; 望月 秀樹*

no journal, , 

The protein, $$alpha$$-synuclein ($$alpha$$-Syn) forms amyloid fibrils. Formation of amyloid fibrils is associated with the pathogenesis of a neuro-degenerative disorder, Parkinson's disease. In order to obtain insights into the role of the protein dynamics in the mechanism of amyloid fibril formation, we carried out quasielastic neutron scattering experiments and characterized the "dynamic" behavior of $$alpha$$-Syn. The measurements on the solution samples of $$alpha$$-Syn in the monomeric and fibril states were carried out using a high energy resolution near-backscattering spectrometer, BL02 (DNA), at MLF/J-PARC, Japan. Differences in the dynamical behavior of the protein were detected between the monomeric and fibril states. Analysis of the spectra obtained suggested an entropy-driven mechanism of amyloid fibril formation.

口頭

Fabrication of Mach-Zehnder optical waveguide structures in PDMS thin films using proton beam writing

狩野 圭佑*; 猿谷 良太*; 川端 駿介*; 新木 潤*; 野口 克也*; 加田 渉*; 三浦 健太*; 加藤 聖*; 佐藤 隆博; 江夏 昌志; et al.

no journal, , 

Proton beam writing (PBW) has been applied to fabricate Mach-Zehnder (MZ) optical waveguides which is expected to be an optical switch with small power consumption, because only one processing of PBW enables us to fabricate such waveguides even inside of plastic materials. Such waveguides were fabricated in thin poly-methyl-methacrylate (PMMA) films by PBW. However, they had low transmittance. In order to fabricate MZ optical waveguides with higher transmittance, PBW was applied to poly-dimethyl-siloxane (PDMS) with higher transparency than PMMA. Thirty-micrometer thick PDMS films formed on silicon wafers were irradiated at different beam fluences using a 750-keV proton microbeam which reaches the half depth of the entire film thickness. The single mode propagation of the fabricated optical waveguide was checked by the 1.55-$$mu$$m light. The observation results showed that the single-mode propagation was detected only for the waveguide fabricated with the fluence of 100 nC/mm$$^2$$ and that the propagated light intensity was higher than that of PMMA. The waveguide structure has been successfully fabricated in thin PDMS films by PBW.

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