ABSTRACT
X-ray diffraction was one of the early methods used by muscle biologists in the middle of the 1900s to investigate the behaviour of muscle contractile proteins and a great deal of fundamental and unambiguous information was obtained. Since then everimproving X-ray methods (stronger X-ray sources, faster X-ray detectors, increased computing power) have enabled the design and execution of ever more sophisticated diffraction experiments on contracting muscles. But there is an experimental challenge with diffraction methods in that the observed patterns need to be interpreted and this can lead to erroneous claims about what the observations mean. Here we illustrate where the power of Xray diffraction lies and also where over-interpretation of X-ray
diffraction patterns can lead down incorrect paths. We show how proper modelling of various parts of the diffraction pattern must be limited to those occasions where the number of observations exceeds the number of independent model parameters to be fitted. We also discuss where future progress can be made.
