Phasing Serial Crystallography Data

The development of serial femtosecond crystallography (SFX) at X-ray free electron lasers (X-ray FELs) allows for the use of tiny protein crystals down to just a few unit cells along an edge, measured at physiological temperatures, and with a time resolution far better than can be achieved with synchrotrons or electron microscopes. The unique properties of the X-ray FEL source has furthermore resulted in the appearance of entirely new ideas for solving the crystallographic phase problem. At the same time, in combination with work on phasing single-particle data (with one bioparticle per shot), SFX has stimulated research into new phasing methods for serial crystallography (SC) at synchrotrons, and protein crystallography in general. In the sense that these new phasing methods depend on the application of constraints, they might be considered developments of traditional “direct methods” such as density modification approaches.