Degree of polarization of light diffracted from resting striated muscle

A laser light diffractometer has been developed to measure directly the total degree of polarization of (alpha t) of light diffracted and randomly scattered from striated muscle fibers. From alpha t the degree of polarization (alpha d) of light diffracted from the periodically arranged contractile filaments is determined. Measurements on single muscle fibers and small fiber bundles indicate that both alpha t and alpha d of the first-order diffraction decrease monotonically with sarcomere length. For the second-order diffraction, alpha t and alpha d exhibit a peak at sarcomere length of about 3.0 micron. A proposed theory based on the anisotropic light scattering efficiencies of the thick and thin filaments can account for the measurements. The comparison between the theory and measurements indicates that the A-band, as well as the I-band, are optically anisotropic.