The indexing ambiguity in serial femtosecond crystallography (SFX) resolved using an expectation maximization algorithm.

ABSTRACT: Crystallographic auto-indexing algorithms provide crystal orientations and unit-cell parameters and assign Miller indices based on the geometric relations between the Bragg peaks observed in diffraction patterns. However, if the Bravais symmetry is higher than the space-group symmetry, there will be multiple indexing options that are geometrically equivalent, and hence many ways to merge diffraction intensities from protein nanocrystals. Structure factor magnitudes from full reflections are required to resolve this ambiguity but only partial reflections are available from each XFEL shot, which must be merged to obtain full reflections from these 'stills'. To resolve this chicken-and-egg problem, an expectation maximization algorithm is described that iteratively constructs a model from the

SUBMITTER: Liu H 

PROVIDER: S-EPMC4224458 | biostudies-literature | 2014 Nov

REPOSITORIES: biostudies-literature