Three-dimensional diffuse x-ray scattering from crystals of Staphylococcal nuclease

We have developed methods for obtaining and characterizing three-dimensional maps of the reciprocal-space distribution of diffuse x-ray scattering from protein crystals, and have used the methods to study the nature of disorder in crystals of Staphylococcal nuclease. Experimentally obtained maps are 99.5% complete in the reciprocal-space resolution range of 10 Å–2.5 Å, show symmetry consistent with the P4(1) space group of the unit cell, and are highly reproducible. Quantitative comparisons of the data with three-dimensional simulations imply liquid-like motions of the protein [Caspar, D. L. D., Clarage, J., Salunke, D. M. & Clarage, M. (1988) Nature (London) 332, 659–662], with a correlation length of 10 Å and a root-mean-square displacement of 0.36 Å.