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Changes in the X-ray reflections from contracting muscle during rapid mechanical transients and their structural
Journal of Molecular Biology
|September 15, 1983
Summary
Rapid muscle length changes synchronize cross-bridge structural cycles, revealing key configurations during contraction. This study uses synchrotron X-rays to observe these dynamic changes in vertebrate striated muscle.
Area of Science:
- Muscle Physiology
- Biophysics
- Structural Biology
Background:
- Vertebrate striated muscle contraction involves asynchronous cross-bridge cycling.
- X-ray diffraction typically averages cross-bridge states, limiting insight into working stroke configurations.
- Understanding cross-bridge mechanics is crucial for muscle function.
Purpose of the Study:
- To investigate cross-bridge structural changes during muscle contraction.
- To synchronize cross-bridge states using rapid length changes.
- To elucidate the role of specific cross-bridge regions in force generation.
Main Methods:
- Utilized synchrotron radiation for high-intensity X-ray diffraction.
- Applied rapid length changes (<1 ms) to isometrically contracting muscles.
- Recorded X-ray patterns with millisecond time resolution.
Main Results:
- Observed significant changes in the 143 Å meridional reflection intensity during rapid length changes.
- These intensity changes correlate with specific configurational alterations in cross-bridges.
- A model suggests the 143 Å reflection originates from myosin heads near the S1-S2 junction.
Conclusions:
- Rapid length changes can synchronize cross-bridge states, enabling detailed structural analysis.
- The 143 Å meridional reflection is sensitive to cross-bridge configuration during the working stroke.
- A significant positional change of myosin head structures relative to actin occurs during the cross-bridge cycle.