Structure Determination from Single-Molecule X‑ray Scattering Images Using Stochastic Gradient Ascent

• Published in: Journal of chemical theory and computation Vol. 21; no. 16; pp. 8227 - 8234
• Main Authors: Schultze, Steffen, Luke, D. Russell, Grubmüller, Helmut
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 26.08.2025
• Subjects: Biomolecular Systems; Biomolecules; Electron density; Free electron lasers; X-ray scattering
• ISSN: 1549-9618; 1549-9626; 1549-9626
• DOI: 10.1021/acs.jctc.5c00748

Scattering experiments using ultrashort X-ray free electron laser pulses have opened a new path for structure determination of a wide variety of specimens, including nanocrystals and entire viruses, approaching atomistic spatial and femtoseconds time resolution. However, random and unknown sample orientations as well as low signal-to-noise ratios have so far prevented a successful application to smaller specimens like single biomolecules. We here present resolution-annealed stochastic gradient ascent (RASTA), a new approach for direct atomistic electron density determination, which utilizes our recently developed rigorous Bayesian treatment of single-particle X-ray scattering. We demonstrate electron density determination at 2 Å resolution of various small proteins from synthetic scattering images with as low as 15 photons per image.