Determining initial and optimal cryoprotectant concentration is often a process of trial and error. One must find suitable cryoprotectant concentrations which stabilize the crystal while at the same time combine with the crystallization reagent to form an amorphous glass.
The Crystal Screen Cryo kits removes the guess work from determining the preliminary glycerol concentration required to mix with the crystallization reagent to form an amorphous glass. Crystal Screen Cryo reagents are formulated with the appropriate amount of glycerol required to form an amorphous glass with each unique reagent composition. Crystals obtained in Crystal Screen Cryo kits will already have a suitable concentration of glycerol in the reagent. This avoids exhaustive empirical searches for preliminary cryoprotectant conditions. From the preliminary cryoprotectant conditions, cryoprotectant concentration can be optimized to minimize mosaic spread and maximize diffraction resolution.
Crystal Screen Cryo kits are biased sparse matrices designed for rapid screening of crystallization conditions of biological macromolecules in the presence of glycerol, the most frequently utilized cryoprotectant. The Crystal Screen Cryo kits utilize the original Crystal Screen™ and Crystal Screen 2™ protocol optimized to include the appropriate concentration of glycerol required to form an amorphous glass at 100°K. The primary screen variables are salt, pH, precipitant (salts, polymers, volatile organics, and non-volatile organics), and cryoprotectant concentration. The screen is a straightforward, effective, and practical kit for determining preliminary crystallization conditions and provides a good starting point for finding suitable cryoprotectant conditions for macromolecular crystals grown in a wide range of reagents. Crystal Screen Cryo is also effective in determining the solubility of a macromolecule in a wide range of precipitants and pH.
Crystal Screen Cryo contains 50 unique reagents, 10 ml each and is based on the sparse matrix formulation first described by Jancarik and Kim in 1991 and refined for cryo by Garman in 1996.
Crystal Screen 2 Cryo contains 48 unique reagents, 10 ml each and is based on the formulation first described by Cudney et al in 1994 and refined for cryo by Snell et al in 2002.
Crystal Screen Cryo HT contains 1 ml each of reagents 1-48 from Crystal Screen Cryo and 48 reagents from Crystal Screen 2 Cryo in a single Deep Well block format.
Ready-to-use reagents are sterile filtered and formulated with ultra-pure Type 1 water, using the highest purity salts, polymers, organics and buffers.
1. Garman, E.F. and Mitchell, E.P., J. Appl. Cryst. (1996) 29, 584- 587.
2. Structure of the single-stranded DNA-binding protein from Streptomyces coelicolor. Stefanic et al, Acta Cryst. (2009) D65, 974-979.
3. The development and application of a method to quantify the quality of cryoprotectant solutions using standard area-detector X-ray images. McFerrin and Snell, J. Appl. Cryst. (2002). 35, 538-545.
4. Cudney, R., Patel, S., Weisgraber, K., Newhouse, Y., and McPherson, A., Acta Cryst. (1994) D50, 414-423.