Date Published: September 01, 2018
Publisher: International Union of Crystallography
Author(s): Douglas H. Juers, Christopher A. Farley, Christopher P. Saxby, Rosemary A. Cotter, Jackson K. B. Cahn, R. Conor Holton-Burke, Kaitlin Harrison, Zhenguo Wu.
Cryosolution thermal contraction is found to have an impact on cryocooled protein and unit-cell volumes and conformations. In some cases, its adjustment can produce higher quality diffraction data.
DMSO: dimethyl sulfoxide.
Diffraction data collection for macromolecular structure determination is commonly carried out at cryogenic temperature, which not only reduces the rate of radiation damage but also allows the kinetic trapping of intermediates for functional studies (Garman & Schneider, 1997 ▸; Weik & Colletier, 2010 ▸). The most common approach for cryo-mounting is to fish the crystal into a small nylon loop or micromount using surface tension and then to rapidly cool the crystal by plunging it into liquid nitrogen or directly transferring it to a nitrogen-vapour stream at ∼100 K (Teng, 1990 ▸; Thorne et al., 2003 ▸).
Our results demonstrate that solvent thermal contraction can impact the thermal response of macromolecular crystals and proteins. The effects appear to be both directly from the temperature change and also from pressure caused by mismatched solvent and pore thermal contraction. Damage from ice formation can include a reduction of cell volumes via what appears to be transport of liquid along solvent channels during cooling. In some cases, adjustment of solution thermal contraction can be used to limit cooling-induced crystal damage.