Modeling analysis of myosin-based meridional X-ray reflections from frog skeletal muscles in relaxed and contracting states.

Analysis of the myosin-based meridional intensity data in the X-ray diffraction patterns of live frog skeletal muscles was performed to propose a more precise model for a myosin crown periodicity and an axial disposition of two-headed crossbridges along the thick filament in a sarcomere. Modeling studies revealed that the thick filament has a mixed structure of two different periodicities of the myosin crossbridge crown arrangement and that the crown periodicity and the axial disposition of crossbridges are altered when muscle goes from the relaxed state to the contracting state. Factors that primarily affect the meridional intensities were examined.