1999 Fiscal Year Final Research Report Summary
Ultra-fast X-ray diffraction studies on the relationship between the structun change extensibility of the actin filaments and force generation in muscle
| Project/Area Number |
09480175
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biophysics
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| Research Institution | Osaka University |
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Principal Investigator |
WAKABAYASHI Katsuzo Graduate School of Engineering Science, Osaka University, Associate Professor, 基礎工学研究科, 助教授 (00029521)
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| Co-Investigator(Kenkyū-buntansha) |
若林 克三 大阪大学, 基礎工学研究科, 助教授 (00029521)
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| Project Period (FY) |
1997 – 1999
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| Keywords | Ultra-fast X-ray diffraction / Synchrotron radiation / Contraction of skeletal muscle / Extensibility of actin filaments / Extensibility of muscle filaments / Actin filaments / Myosin filaments / Force generation in muscle |
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| Research Abstract |
In order to understand the relationship between the mechanical properties of thin actin-containing filaments and force generation in skeletal muscle, the fast X-ray diffraction studies were performed by using synchrotron radiation. The principal results were described below.
(1) The relation between the extensibility of the actin filaments and force generated in muscle was linear, establishing that the actin filament has a purely elastic property. Such an extensibility of the actin filaments was closely associated with a torsional motion of the actin monomers in the filament and its time course of the change occurred with the development of force.
(2) Upon the initial activation, the thin actin filaments became shortened slightly but significantly. Considering this result, the net extensibility of the actin filaments in muscle under the maximum force generation was determined to about 0.35%.
(3) When the ramp length stretch was applied to a contracting muscle, the intensity decrease of the myosin meridional reflections and their axial spacing change run parallel to the change in force, implying that the structural alteration of the myosin crossbridges is coupling with the force-generation mechanism.
In this research, firm experimental evidence was provided for the elastic properties and structural changes of the thin actin filaments in active muscle. Based on these new results, the molecular model for muscle contraction was discussed in a combination of peculiar conformational changes of both actin and myosin.
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