Time-resolved X-ray diffraction studies of cross-bridge movement and their interpretation.

The purpose of these studies has been to obtain information about the structural behaviour of the cross-bridges during contraction. Since there are so few reflections still present in the part of the X-ray diagram produced by cross-bridges in a contracting muscle they cannot on their own give a detailed picture. However, they can give information of a more general nature - much in the same way as measurements of tension may do, for example - and the patterns can also tell us what structural regularities are no longer present during contraction. The experiments which I will describe have been carried out in nearly all cases on frog sartorius muscles using synchrotron radiation as an intense X-ray source. The necessary facilities were provided by the European Molecular Biology Laboratory Outstation on the storage ring DORIS at DESY Hamburg. The results to which I will refer have in many cases already been described in papers published or in press (Huxley, 1979; Huxley, Faruqi , Bordas , Koch and Milch , 1980; Huxley, Simmons, Faruqi , Kress , Bordas and Koch, 1981; Huxley, Faruqi , Kress , Bordas and Koch, 1982), to which reference may also be made for experimental details.