AN OPEN-FLOW CRYOGENIC COOLER FOR SINGLE-CRYSTAL DIFFRACTION EXPERIMENTS

A simple, low-cost and efficient open-flow cryogenic cooling system ha s been constructed for crystallographic data collection from flash-coo led protein crystals on the rotation-camera station at the Stanford Sy nchrotron Radiation Laboratory. A constant temperature of less than 10 0 K at the crystal position can be maintained for an indefinite period of time. A small heater surrounding the delivery nozzle and another b etween the sample crystal and the sample support are used to prevent t he formation of ice. The system includes an automatic filling capabili ty so that the device can be run unattended for up to approximately on e week.