Protein Crystals Grown by Means of Porous Materials are of better X-ray Diffraction Quality

What is it about?

Even nowadays, X-ray crystallography is the paramount method in protein structure determination. (The proof is that X-ray diffraction studies account for 89% of structures deposited in the Protein Data Bank). However, protein crystals of sufficiently high diffraction quality are notoriously difficult to grow. Importantly, this problem has been mitigated using porous materials: just sufficient for crystal nucleation supersaturation occurs in some pores. But the volume of the protein crystal in the pore is negligible in comparison to its volume outside the pore. Therefore, the latter determines the diffraction quality of the protein crystal. In this paper, considering the molecular-scale mechanism of growth of protein crystals initially inside pores and subsequently outside them, we show that the growth process is favored energetically in both cases. It is explained why, using porous materials, the diffraction quality of protein crystals is improved: The reason is that the supersaturation under which the crystals nucleate in-side pores and subsequently grow outside them is lower as compared to the one that is needed for the usual protein crystallization.

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Why is it important?

The elucidation of the molecular-scale mechanism of growth of protein crystals, both inside pores and outside them, can contribute for growing crystals of improved X-ray diffraction quality.