ANALYSIS OF EQUATORIAL X-RAY-DIFFRACTION PATTERNS FROM MUSCLE-FIBERS - FACTORS THAT AFFECT THE INTENSITIES

Previously we have shown that cross-bridge attachment to actin and the radial position of the myosin heads surrounding the thick filament ba ckbone affect the equatorial x-ray diffraction intensities in differen t ways (Yu, 1989). In the present study, other factors frequently enco untered experimentally are analyzed by a simple model of the filament lattice. It is shown that the ordering/disordering of filaments, latti ce spacing changes, the azimuthal redistributions of cross-bridges, an d variations in the ordered/disordered population of cross-bridges sur rounding the thick filaments can distinctly affect the equatorial inte nsities. Consideration of Fourier transforms of individual components of the unit cell can provide qualitative explanations for the equatori al intensity changes. Criteria are suggested that can be used to disti nguish the influence of some factors from others.