Development of a cooling device for cryogenic X-ray and neutron Crystallography

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An open-flow cryostat using helium gas has been developed for cryogenic X-ray crystallography. The device is composed of a cryostat and a heat exchange apparatus, and dry nitrogen gas is supplied for shielding the cooled helium gas from atmosphere. The lowest temperature reached by the device is 35 K within a fluctuation of ±0.5 K at a flow rate of 6 litter/min. This device is easy to operate and enables to study crystal structures and the temperature-dependent phenomena occurring in biological macromolecules and materials above 35 K. In addition, The techniques in cryogenic experiments around the liquid nitrogen temperature have been applied to the structural determinations of various enzymes, the hydration structure analysis of proteins and the investigation of internal vibrational properties of proteins around the glass-transition temperature.