P212121

Cryocrystallography is the collection of crystallographic data at cryogenic temperatures primarily with the use of liquid nitrogen. The following advantages and disadvantages are comparing cryogenic vs. room temperature data collection.

Advantages

1) Reduced Radiation Damage: when compared to room temperature collection
2) Fewer Crystals: as to be expected if the radiation damage is reduced the crystal lifetime is increased therefore reducing number of crystals
3) Better Data: increased resolution, I/sigma, redundancy, reduced B values and stronger anomalous signal
4) Better Crystals: protein crystals can be selected at opportune times during the crystallization process (possibly avoid dissolving or cracking) as well as be easily transported within cryogenic dewars

Disadvantages

1) Icing: even if icing occurs it may be possible to salvage the collection during data processing
2) Cryoprotectants: many protein crystals require the use of a cryoprotectant (the most popular is the use of 20-25 % glycerol) prior to being exposed to the cold stream
3) Increased mosaicity: this can be reduced with the proper cryoprotectant as well as mounting technique (ref pg. 32)
4) Non-isomorphism: unit cell size may vary (ref)
5) Cost of equipment: include in grant applications or have at least two bake sales