As a bit of an aside, my current "reference crystal" of choice is a Germanium Oxide with a 51.3Ang cubic cell. see here: http://www.nature.com/nature/journal/v437/n7059/full/nature04097.html It is much more raditation hard than protein so I can do repeated measurements in the synchrotron beam without radiation damage becoming a factor. It is also physically harder than protein crystal making it easy to break up into sizes of choice and there is no worry about keeping it optimally hydrated.
Cheers, Danny DLS I24 Micro-focus Beamline
