Experiments on striated muscle have been carried out at the EMBL Outstation at DESY, Hamburg, using the electron-positron storage ring DORIS as a high-intensity X-ray source. The low-angle reflections from the myosin cross-bridges could be recorded more than 1,000 times more rapidly than with the best conventional X-ray sources, and could be followed during contraction with a time resolution of 10 ms.

A useful geometry is presented for analyzing X‐ray diffraction patterns from a rotating crystal. From the basic diffraction condition, equations are derived for determining which reflections will appear in a given rotation range and where they will be found on the detector. Several procedures for indexing rotation photographs from protein crystals are discussed and the application of two of them to an X‐ray diffraction study of hen egg‐white lysozyme is described.

A sensitive, efficient image intensifier-TV x-ray detector is described that has been optimized for a large class of diffraction studies of biological structures. All of the major components are commercially available. The system is well suited to measuring the intensity of diffraction patterns that are weak, or changing with time. Because there is no count rate limitation, it is particularly well suited for studies utilizing the high fluxes of synchrotron sources.

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