DESIGN OF AN INVERTED SPINDLE AXIS FOR FROZEN CRYSTAL SCREENING AND STORAGE

For biological macromolecules, X-ray diffraction data collection at te mperatures close to that of liquid nitrogen greatly reduces radiation damage and allows an almost unlimited number of data to be collected f rom a single crystal. Single-axis instruments are common and are very often configured with the spindle axis vertical and pointed upwards (e .g. the R-axis image-plate diffractometer from Molecular Structure Cor poration). This geometry allows a crystal to be frozen after it is mou nted, but it is difficult to use prefrozen crystals or to remove and s tore crystals once an initial set of data has been collected. Such pre screening is very useful for efficient synchrotron data collection. In this paper, a device is presented that accomplishes an inversion of t he spindle axis, allowing easy transfer of crystals to and from liquid nitrogen and a data collection run with Phi sweeps. This device is re adily interchangeable with the standard goniometer mount.