A Monte Carlo calculation of the interparticle interference in small-angle X-ray scattering

In solution small-angle X-ray scattering data, the lowest-angle region is affected by interparticle correlations and potentially provides information concerning particle-particle interactions in solution, such as overall electrostatic interaction- attractive or repulsive - and tendency to form aggregates. A method is presented, based on a Monte Carlo approach, to calculate the interparticle interference for a solution of particles of arbitrary shape interacting through a simple two-particle hard-core potential. The method provides a basis for a quantitative analysis of the concentration-dependent scattering in the low-angle region. It has been used to study the relative effects of interparticle interference and particle dimerization in the scattering profiles for the proteins troponin C and lysozyme. The calculation may be generalized to include a more physically realistic potential.