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Tetragonal thermolysin (with 50% xylose) plunge cooled in liquid nitrogen to 77 KTetragonal thermolysin (with 50% xylose) plunge cooled in liquid nitrogen to 77 K
Structural highlights
Function[THER_BACTH] Extracellular zinc metalloprotease. Publication Abstract from PubMedCryocooling for macromolecular crystallography is usually performed via plunging the crystal into a liquid cryogen or placing the crystal in a cold gas stream. These two approaches are compared here for the case of nitro-gen cooling. The results show that gas stream cooling, which typically cools the crystal more slowly, yields lower mosaicity and, in some cases, a stronger anomalous signal relative to rapid plunge cooling. During plunging, moving the crystal slowly through the cold gas layer above the liquid surface can produce mosaicity similar to gas stream cooling. Annealing plunge cooled crystals by warming and recooling in the gas stream allows the mosaicity and anomalous signal to recover. For tetragonal thermolysin, the observed effects are less pronounced when the cryosolvent has smaller thermal contraction, under which conditions the protein structures from plunge cooled and gas stream cooled crystals are very similar. Finally, this work also demonstrates that the resolution dependence of the reflecting range is correlated with the cooling method, suggesting it may be a useful tool for discerning whether crystals are cooled too rapidly. The results support previous studies suggesting that slower cooling methods are less deleterious to crystal order, as long as ice formation is prevented and dehydration is limited. A comparison of gas stream cooling and plunge cooling of macromolecular crystals.,Harrison K, Wu Z, Juers DH J Appl Crystallogr. 2019 Aug 23;52(Pt 5):1222-1232. doi:, 10.1107/S1600576719010318. eCollection 2019 Oct 1. PMID:31636524[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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