X-ray analysis and the problem of muscle

Abstract The present-day picture of muscle is briefly as follows: muscle is a machine for converting chemical energy into mechanical work; the ‘moving parts’ of this machine are built up of two proteins, actin and myosin; the known energy-producing reaction most closely linked to the contractile process is the dephosphorylation of adenosine triphosphate (ATP). In the present studies, low-angle X-ray diffraction technique has been used to study the molecular structure of these two proteins, actin and myosin, and their arrangement in living muscle under various conditions.