X-Ray Diagrams from Skeletal Muscle in the Presence of ATP Analogs

Structural studies on skeletal muscle have revealed many of the events which must take place in a contraction. The outward movement of myosin cross-bridges to the actin filaments when a muscle goes into rigor (Huxley, 1968) is matched to some extent in a contracting, live muscle (Haselgrove, 1970). Similarly, the loss in rigor of the myosin layer lines so typical of live muscle is partially paralleled during contraction (Huxley and Brown, 1967; Haselgrove, 1970), indicating an increased disorder of the cross-bridges. These results have been interpreted in simple terms: The myosin cross-bridges in a resting live muscle are located on average very near the thick filament, their position determined by the ordered arrangement of the LMM (light meromyosin) parts of the...