Advances in digital topography for characterizing imperfections in protein crystals

A system which joins digital topography with fine φ-sliced reflection profiling has been developed and applied to cryocrystallography. In this demonstration, fifteen fine φ-sliced reflection profiles with corresponding topographic sequences are evaluated: twelve reflections from a crystal at cryogenic temperatures and three reflections from a room-temperature crystal. The digitally collected data show results comparable with film, albeit at a lower resolution, but are acquired at a substantially higher rate. Additionally, anti-blooming circuitry in the CCD was tested and shown to provide useful data even when pixels were overloaded.