Partial orientation retrieval of proteins from X-ray free-electron-laser induced explosions for single particle imaging

Single Particle Imaging techniques at X-ray lasers have made significant strides, yet the challenge of determining the orientation of freely rotating molecules during delivery remains. In this study, we propose a novel approach to partially retrieve the relative orientation of proteins exposed to ultrafast X-ray pulses by analyzing the fragmentation patterns resulting from Coulomb explosions. We simulate these explosions for 85 proteins in the size range 100 - 4000 atoms using a hybrid Monte Carlo/Molecular Dynamics approach and capture the resulting ion ejection patterns on two virtual detectors. We exploit information from the explosion to infer orientations of proteins at the time of X-ray exposure. Our results demonstrate that partial orientation information can be extracted, particularly for larger proteins. We conclude that knowledge on ion data from X-ray laser induced explosions can directly provide the sample's relative orientation, complementary to traditional orientation-retrieval algorithms based on diffraction patterns.