Labelling of Thin Filaments by Myosin Heads in Contracting and Rigor Vertebrate Skeletal Muscles

A method of crystallographic analysis to identify myosin heads interacting with specific actin sites in vertebrate striated muscles is described. It is based on a Fourier transform of a helix in which probability of occurrence of subunits varies periodically. It predicts the presence of layer-lines at 1/24 and 1/10.4 nm^-1 which are experimentally observed in contracting and rigor vertebrate striated muscles, showing that the myosin heads are interacting with specific sites on actin but are still maintaining their average 14.5 nm axial periodicity.