Using cryoloops for X-ray data collection from protein crystals at room temperature: A simple applicable method

Although cryoloops are now routinely used for X-ray data collection from protein crystals in cryocooling condition, it is still necessary to collect X-ray diffraction data from protein crystals at room temperature under such circumstances as to find resolution limit and/or to avoid damage of protein crystals at cryogenic temperature (e.g. 100 K). Here, we show that a cryoloop, which is accompanied by a glass capillary cap to maintain humid environment of crystal in the cryoloop, can be used not only to examine protein or non-protein crystals but also to collect X-ray diffraction data for structural analysis from protein crystals at room temperature. The size of cryoloop should be carefully chosen so that the crystal does not move in the cryoloop. This crystal mounting method can be time-saving compared to the traditional method to mount a crystal in a glass capillary tube.