Abstract
Single particle imaging at x-ray free electron lasers (XFELs) has the potential to determine the structure and dynamics of single biomolecules at room temperature. Two major hurdles have prevented this potential from being reached, namely, the collection of sufficient high-quality diffraction patterns and robust computational purification to overcome structural heterogeneity. We report the breaking of both of these barriers using gold nanoparticle test samples, recording around 10 million diffraction patterns at the European XFEL and structurally and orientationally sorting the patterns to obtain better than 3-nm-resolution 3D reconstructions for each of four samples. With these new developments, integrating advancements in x-ray sources, fast-framing detectors, efficient sample delivery, and data analysis algorithms, we illuminate the path towards sub-nanometer biomolecular imaging. The methods developed here can also be extended to characterize ensembles that are inherently diverse to obtain their full structural landscape.
Highlights
The determination of the structures of biomolecules at atomic resolution requires bright sources of radiation, which are energetic enough to degrade the object under obtained within the exposure that the sample can tolerate
We report the breaking of both of these barriers using gold nanoparticle test samples, recording around 10 million diffraction patterns at the European x-ray free electron lasers (XFELs) and structurally and orientationally sorting the patterns to obtain better than 3-nm-resolution 3D reconstructions for each of four samples
Single particle imaging (SPI) at XFELs consists of collecting coherent diffraction patterns from individual particles intersecting bright XFEL pulses
Summary
The determination of the structures of biomolecules at atomic resolution requires bright sources of radiation, which are energetic enough to degrade the object under. Proof-of-principle SPI experiments on biological particles [8,9,10,11,12,13,14] have highlighted the challenges of the approach, i.e., the recording of a large number of patterns, all with sufficiently low background, and from structurally homogeneous samples. ASample names refer to their nominal shape (octahedron or cube) and edge length in nanometers. bThe three numbers correspond to values for 0.28 MHz, 0.55 MHz, and 1.1 MHz intra-train repetition rates, respectively. cThere was no clear sign of spherical particles for the cub sample. dThe first number is the azimuthal average resolution, while numbers in parentheses show minimum and maximum values, respectively
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