| Project/Area Number |
60480512
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
生物物性学
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| Research Institution | Osaka University |
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Principal Investigator |
WAKABAYASHI Katsuzo Faculty of Engineering Science, Osaka University, 基礎工学部, 助手 (00029521)
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| Project Period (FY) |
1985 – 1986
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| Project Status |
Completed (Fiscal Year 1986)
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| Budget Amount *help |
¥5,600,000 (Direct Cost: ¥5,600,000)
Fiscal Year 1986: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1985: ¥5,100,000 (Direct Cost: ¥5,100,000)
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| Keywords | Muscle Contraction / Actin Filament / Synchrotron Radiation / Imaging Plate / Fast X-Ray Diffraction / Integrating Area Detector / Time-Resolved X-Ray Diffraction / カエル骨格筋 |
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| Research Abstract |
Time-resolved X-ray diffraction studies have been made on the 5.9 nm and 5.1 nm actin layer lines from frog skeletal muscles during an isometric tetanus, using synchrotron radiation. The integrated intensities of these actin layer lines were found to increase during a tetanus by 30-50% for the 5.9 nm reflection and about 70% for the 5.1 nm reflection of the resting values. The intensity increase of both reflections was greater than that taking place in the transition from rest to rigor state. The intensity change of the 5.9 nm reflection preceded those of the myosin 42.9 nm off-meridional reflection and equatorial reflections, as well as the isometric tension. The intensity profile of the 5.9 nm layer line during contraction was found to be different from that observed in the rigor state.
A conceptually new type of an integrating area X-ray detector (an imaging plate) was used in a diffraction study of muscle contraction. The high sensitivity and wide dynamic range of the imaging plate resulted in a dramatic reduction in the exposure time, making it possible to record very clear two-dimensional X-ray diffraction patterns of up to 2.0 nm axial spacing from a contracting frog skeletal muscle as little as 10 seconds using synchrotron radiation. During contraction of a frog skeletal muscle, most of actin layer lines increased in intensity without noticeasble changes in their peak positions along the layer line and axial spacing. The layer-line intensity distributions of actin layer lines were measured. The structural analyses were made by model-calculation to obtain the best-fit to the observed intensities. The results indicated that during contraction the changes of the domain structure in the actin subunit as well as the positional change of tropomyosin molecules take place by the interaction with myosin heads as well as the binding of Ca ions to troponin.
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