FMAPIq: Fast calculation of small-angle scattering profiles from dense protein solutions

Method at a Glance

FMAPIq uses MAEPPI (many-protein atomistic energy from precomputed pair interaction) to drive Monte Carlo simulations of dense protein solutions and uses Sim2Iq to calculate small-angle scattering profiles, I(q). In MAEPPI, we first precompute the interaction energies of a protein pair at various relative displacements and relative orientations, and store them in a lookup table. In simulations of a many-protein system, we then obtain the total energy by looking up and adding up the interaction energies of individual protein pairs. The fast calculation of protein pair energies was made possible by using the FMAP method, which is based on fast Fourier transform (FFT). Likewise, Sim2Iq calculations are sped up by applying FFT to simulation snapshots. FMAPIq maintains atomic-level accuracy while achieving the speed of Lennard-Jones particles.