HC-Lab Humidity Controller

Controlled crystal dehydration

Crystal dehydration can considerably improve the X-ray diffraction quality for poorly diffracting macromolecular crystals and finally, lead to diffraction data with higher resolution.

The below image shows a series of diffraction patterns which were taken during a dehydration experiment on a laboratory home source and a single crystal. The sample’s relative humidity was set with Arinax’s Humidity Controller for two different crystal orientations,  = 0° and  = 90°.

For each crystal orientation the diffraction data was recorded for successively decreasing relative humidity values. This experiment resulted in a resolution improvement from 8 Å at RH = 99% to 4 Å at RH = 96%.

Automatic drop size tracking

The HC-Lab control software exploits sample images, e.g. delivered by the goniometer’s video microscope. Depending on the RH set point the drop of mother liquor surrounding the crystal will shrink (low RH), increase its diameter (high RH) or remain stable in size (equilibrium RH). The drop size is constantly monitored by the control software via image recognition and dynamically plotted in a time diagram together with the actual RH value.

The sample visualization and the monitoring over time of different experimental parameters like drop size, sample temperature and RH value gives an unprecedented degree of control over dehydration experiments. Python scripting can be used for programming experiment cycles with varying parameters and successive X-ray data collection.