An automated system to mount cryo-cooled protein crystals on a synchrotron beamline, using compact sample cassettes and a small-scale robot

An automated system for mounting and dismounting pre-frozen crystals has been implemented at the Stanford Synchrotron Radiation Laboratory (SSRL). It is based on a small industrial robot and compact cylindrical cassettes, each holding up to 96 crystals mounted on Hampton Research sample pins. For easy shipping and storage, the cassette fits inside several popular dry-shippers and long-term storage Dewars. A dispensing Dewar holds up to three cassettes in liquid nitrogen adjacent to the beamline goniometer. The robot uses a permanent magnet tool to extract samples from, and insert samples into a cassette, and a cryo-tong tool to transfer them to and from the beamline goniometer. The system is simple, with few moving parts, reliable in operation and convenient to use.