Abstract
Cryocrystallography is a technique that is used more often than room-temperature data collection in macromolecular crystallography. One of its advantages is the significant reduction in radiation damage, which is especially useful in synchrotron experiments. Another advantage is that cryopreservation provides simple storage of crystals and easy transportation to a synchrotron. However, this technique sometimes results in the undesirable adhesion of frost to mounted crystals. The frost produces noisy diffraction images and reduces the optical visibility of crystals, which is crucial for aligning the crystal position with the incident X-ray position. To resolve these issues, a computer-controlled device has been developed that drizzles liquid nitrogen over a crystal to remove frost. It was confirmed that the device works properly, reduces noise from ice rings in diffraction images and enables the centering of crystals with low visibility owing to frost adhesion.
Highlights
In macromolecular crystallography (MX) using a synchrotron, cryocrystallography is commonly used to obtain high-quality diffraction data (Hope, 1988; Parkin & Hope, 1998; Rodgers, 1994; Garman & Schneider, 1997)
The sample temperature is maintained at 100 K or below using a cryostream device and is important for reducing radiation damage to the samples and automating sample exchange (Murakami et al, 2012)
A major obstacle in this technique is ice or frost contamination in or on the flash-cooled droplets containing crystals. This deteriorates the diffraction images by the addition of reflections derived from ice diffraction
Summary
In macromolecular crystallography (MX) using a synchrotron, cryocrystallography is commonly used to obtain high-quality diffraction data (Hope, 1988; Parkin & Hope, 1998; Rodgers, 1994; Garman & Schneider, 1997). To increase the temperature of crystals, blocking of the cold stream is suitable for automatic operation (Yeh & Hol, 1998) and is applied at the SPring-8 MX beamlines This defrosting method can effectively remove frost, but some fragile samples may be damaged by the temperature change. There is a method that involves rinsing the sample pins in the liquid nitrogen (LN2) dewar with a sample-handling robot; there is the possibility of frost adhering again (Soltis et al, 2008) Another method involves flashing a refrigerant medium such as liquid nitrogen over the crystal (Pflugrath, 2004; Warkentin & Thorne, 2007; Garman & Owen, 2006). We describe its configuration and the results of diffraction experiments with and without the device
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