Improved technique for calculating X‐ray scattering intensity of biopolymers in solution: Evaluation of the form, volume, and surface of a particle

Abstract

AbstractAn improved cube method has been developed for calculating the intensity of diffuse x‐ray scattering of macromolecules in solution using a certain set of their atomic coordinates. The technique is based on the ideas of B. Lee and F. M. Richards [(1971) J. Mol. Biol. 55, 374–400] and Richards [(1977) Annu. Rev. Biophys. Bioeng. 6, 151–176] on the possibility of estimating the molecular and accessible surface of a particle by “rolling” a sphere, simulating a water molecule, on its molecular surface. It is shown that this technique is more advantageous than earlier versions of the cube methods. The improved technique for calculating scattering curves was utilized for several globular proteins, and for the first time, reliable scattering curves were obtained for protein‐“bound” water complexes. In the case of globular proteins and tRNA, this technique has permitted a strict evaluation of their accessible surfaces, their volumes, and, apparently for the first time, their complete molecular surfaces.