Calculation of small-angle scattering profiles using Monte Carlo simulation

A method for calculating small-angle scattering profiles using Monte Carlo simulation of the scattering volume is described. From the simulated volume the distance distribution function is calculated directly and a simple Fourier transformation produces the scattering profile. The method is easy to apply to molecules of any shape and composition. Here it is tested against the theoretical profile for a sphere and for an ellipsoid. Finally, the method is applied to a scatterer composed of three spheres connected by a long rod (a model for the biomolecule fibrinogen).