High Resolution Protein Crystals Using an Efficient Convection-Free Geometry

• Published in: Crystal growth & design 2013-02, Vol.13 (2), p.775-781
• Main Authors: Adawy, Alaa, Rebuffet, Etienne, Törnroth-Horsefield, Susanna, de Grip, Willem J, van Enckevort, Willem J. P, Vlieg, Elias
• Format: Article
• Language: English
• Subjects: atomic-force microscopy; Biochemistry and Molecular Biology; Biokemi och molekylärbiologi; bovine insulin; crystallization; egg-white lysozyme; impurity distribution; insulin crystals; microgravity; purification; quality
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg301497t

Macromolecular crystallography is the most direct and accurate approach to determine the three-dimensional structure of biological macromolecules. The growth of high quality single crystals, yielding diffraction to the highest X-ray resolution, remains a bottleneck in this methodology. Here we show that through a modification of the batch crystallization method, an entirely convection-free crystallization environment is achieved, which enhances the purity and crystallinity of protein crystals. This is accomplished by using an upside-down geometry, where crystals grow at the “ceiling” of a growth-cell completely filled with the crystallization solution. The “ceiling crystals” experience the same diffusion-limited conditions as in space microgravity experiments. The new method was tested on bovine insulin and two hen egg-white lysozyme polymorphs. In all cases, ceiling crystals diffracted X-rays to resolution limits beyond that for other methods using similar crystallization conditions without further optimization. In addition, we demonstrate that the ceiling crystallization method leads to crystals with much lower impurity incorporation.