Inferences concerning crossbridges from work on insect muscle.

This paper presents a number of separate results concerning crossbridge attachment: [1] X-ray diffraction from live bumble bee flight muscle shows a set of layer lines distinct from that of relaxed Lethocerus, in which the apparent myosin helix is shorter than that of the actin. [2] Rigor crossbridges of Lethocerus are not rotatable by stretch. [3] Rabbit and Lethocerus fibres in rigor relaxed by ATP at -35 degrees C show evidence of non-rigor crossbridge attachment.