Automation and Experience of Controlled Crystal Dehydration: Results from the European Synchrotron HC1 Collaboration

Controlled dehydration of macromolecular
crystals can lead to significant
improvements in crystalline order, which often manifests itself in
higher diffraction quality. Devices that can accurately control the
humidity surrounding crystals on a beamline have led to this technique
being increasingly adopted as experiments become easier and more reproducible.
However, these experiments are often carried out by trial and error,
and in order to facilitate and streamline them four European synchrotrons
have established a collaboration around the HC1b dehydration device.
The MAX IV Laboratory, Diamond Light Source, BESSY II, and the EMBL
Grenoble Outstation/ESRF have pooled information gathered from user
experiments, and on the use of the device, to propose a set of guidelines
for these experiments. Here, we present the status and automation
of the installations, advice on how best to perform experiments using
the device, and an analysis of successful experiments that begins
to show some trends in the type of protocols required by some systems.
The dehydration methods shown are applicable to any device that allows
control of the relative humidity of the air surrounding a macromolecular
crystal.