Bayesian algorithms for recovering structure from single-particle diffraction snapshots of unknown orientation: a comparison

TL;DR

This paper compares two Bayesian algorithms used for reconstructing the structure of particles from single diffraction snapshots with unknown orientations, highlighting their similarities and performance limitations.

Contribution

It reveals that two recent methods are fundamentally the same approach and analyzes the factors limiting their effectiveness.

Findings

Both algorithms are different implementations of the same fundamental method.

Performance is limited by low signal levels (~10-2 photons/pixel).

Identifies primary factors affecting algorithmic performance.

Abstract

The advent of X-ray Free Electron Lasers promises the possibility to determine the structure of individual particles such as microcrystallites, viruses and biomolecules from single-shot diffraction snapshots obtained before the particle is destroyed by the intense femtosecond pulse. This program requires the ability to determine the orientation of the particle giving rise to each snapshot at signal levels as low as ~10-2 photons/pixel. Two apparently different approaches have recently demonstrated this capability. Here we show they represent different implementations of the same fundamental approach, and identify the primary factors limiting their performance.