Section: New Results

Pepsi-SAXS : an adaptive method for rapid and accurate computation of small angle X-ray scattering profiles

Participant : Sergei Grudinin.

We developed a new method called Pepsi–SAXS that calculates small angle X-ray scattering profiles from atomistic models. Our method is based on the multipole expansion scheme and is significantly faster and more precise compared to other tested methods. In particular, using the Nyquist–Shannon–Kotelnikov sampling theorem, we adapt the multipole expansion order to the size of the model and the resolution of the experimental data. We argue that using the adaptive expansion order, our method has the same quadratic dependence on the number of atoms in the model as the Debye-based approach, however, with a much smaller prefactor in the computational complexity.

We have systematically validated our method on an excessive set of over fifty models collected from the BioIsis and SASBDB databases. Using a laptop, we demonstrated that Pepsi-SAXS is about 9, 33 and 43 times faster compared to CRYSOL, FoXS and the 3D-Zernike method in SAStbx, correspondingly, when tested on data from the BioIsis database, and is about 5, 18 and 23 times faster compared to CRYSOL, FoXS and SAStbx, correspondingly, when tested on data from SASBDB. On average, Pepsi-SAXS achieves 17% smaller value of $\chi$ compared to CRYSOL and 15% smaller value of $\chi$ compared to FoXS for BioIsis profiles, and 6% smaller value of$\chi$ compared to CRYSOL and 19% smaller value of $\chi$ compared to FoXS for SASBDB profiles.