Section: New Results

Reconstructing molecular shapes from SAXS data

We are working on a novel method to reconstruct the three-dimensional shape of a molecule from low-resolution experimental data. The structural data we are currently focusing on is obtained through small-angle X-ray scattering (SAXS) experiments, but we plan to also consider small-angle neutron scattering (SANS) data. Our ab initio reconstruction method is inspired by iterative phase-retrieval algorithms that can produce an image for an object when only the amplitudes of its Fourier transform are known and the phases are unknown. In our context, the X-ray scattering amplitudes associated with a molecule are the Fourier transform of its electron density. The novelty of our approach resides in the use of spherical harmonics expansions, which will allow performing the whole reconstruction process in Fourier space—contrary to existing methods that iterate between Fourier space and real space—for an improved computational efficiency. Our method is being implemented within the software PEPSI (polynomial expansions of protein structures and interactions).