  An improved analysis for single particle imaging (SPI) experiments, using the
limited data, is presented here. Results are based on a study of bacteriophage
PR772 performed at the AMO instrument at the Linac Coherent Light Source (LCLS)
as part of the SPI initiative. Existing methods were modified to cope with the
shortcomings of the experimental data: inaccessibility of information from the
half of the detector and small fraction of single hits. General SPI analysis
workflow was upgraded with the expectation-maximization based classification of
diffraction patterns and mode decomposition on the final virus structure
determination step. The presented processing pipeline allowed us to determine
the three-dimensional structure of the bacteriophage PR772 without symmetry
constraints with a spatial resolution of 6.9 nm. The obtained resolution was
limited by the scattering intensity during the experiment and the relatively
small number of single hits.
