Sample size: an important parameter in flash-cooling macromolecular crystallization solutions

• Published in: Journal of applied crystallography 2005-06, Vol.38 (3), p.412-419
• Main Authors: Chinte, U., Shah, B., DeWitt, K., Kirschbaum, K., Pinkerton, A. A., Schall, C.
• Format: Article
• Language: English
• Subjects: Analytical, structural and metabolic biochemistry; Biological and medical sciences; cryocrystallography; flash-cooling; Fundamental and applied biological sciences. Psychology; In solution. Condensed state. Thin layers; Miscellaneous; Molecular biophysics; Physico-chemical properties of biomolecules; Properties of solutions; aggregation and crystallization of macromolecules; Proteins; vitrification
• ISSN: 1600-5767; 0021-8898; 1600-5767
• DOI: 10.1107/S0021889805005029

The effect of sample size on flash‐cooling was assessed using an assortment of Hampton Screen I solutions (Hampton Research). These were cryogenically cooled to ascertain the minimum glycerol concentration needed for vitrification of solutions. Solutions were `flash‐cooled' in 1.0, 0.5 and 0.1 mm commercial cryoloops, using a 100 K nitrogen stream generated by an Oxford 600 Cryostream. The loops were visually examined and then X‐ray diffraction data were collected and evaluated for ice formation. The glycerol concentration needed for vitrification was found to decrease significantly as sample size decreased; detailed key data are presented in tabular form. Glass transition temperatures, Tg, were measured for solutions leading to successful vitrification in the 1 mm cryoloop. The trends in the required concentration of glycerol and resultant Tg can be understood through a simplified heat‐transfer analysis. This analysis points to a critical cooling time period for successful vitrification.