Structure from fleeting illumination of faint spinning objects in flight

Moves are afoot to illuminate particles in flight with powerful X-ray bursts, to determine the structure of single molecules, viruses and nanoparticles. This would circumvent important limitations of current techniques, including the need to condense molecules into pure crystals. Proposals to reconstruct the molecular structure from diffraction ‘snapshots’ of unknown orientation, however, require ∼1,000 times more signal than available from next-generation sources. Using a new approach, we demonstrate the recovery of the structure of a weakly scattering macromolecule at the anticipated next-generation X-ray source intensities. Our work closes a critical gap in determining the structure of single molecules and nanoparticles by X-ray methods, and opens the way to reconstructing the structure of spinning, or randomly oriented objects at extremely low signal levels. An algorithm that reconstructs the structure of an object in flight from the diffraction pattern generated by exposing it to an ultrashort burst of X-rays should enhance the potential of free-electron lasers for studying individual molecules, virus and nanoparticles.