Approaches to physical fitness and sports medicine through X-ray diffraction analysis of striated muscle

抄録

X-ray diffraction analysis is a method to obtain information about periodically repeated structures. When striated muscle is irradiated with X-ray, many of the reflections and the layer lines, which convey information about molecular structures within the muscle fiber, are obtained without chemical modification. Two of the strong equatorial reflections, 1,0 reflection arising from a thick filament array and 1,1 reflection arising from a thick and thin filament array appear on the equator giving information about distance and mass distribution on a radial plane. Thus a 1,1/1,0 intensity ratio is a good index of radial distribution of myosin heads. Meridional reflections and layer lines, such as a myosin reflection of the 14.3 nm repeat and myosin or actin layer lines, give information about longitudinal arrangement of the molecules. Since they are affected by the movement of the myosin heads and the shifting motion of troponin-tropomyosin on the actin filament, they can be used to detect conformational changes of contractile and regulatory systems upon muscle activation. The X-ray diffraction method has been applied to yield fruitful results for many problems such as muscle atrophy by disuse, functional modulation by myosin regulatory light chain phosphorylation, differential characteristics of slow and fast skeletal muscle structure, and pathogenesis of some types of the familial myopathy. The approach using X-ray diffraction analysis will continuously serve as a potent tool for resolving problems in the field of physical fitness and sports medicine.