The MORPHEUS II protein crystallization screen

High-quality macromolecular crystals are a prerequisite for the process of protein structure determination by X-ray diffraction. Unfortunately, the relative yield of diffraction-quality crystals from crystallization experiments is often very low. In this context, innovative crystallization screen formulations are continuously being developed. In 2009, Fabrice Gorrec from the MRC Laboratory of Molecular Biology in Cambridge (LMB) published developments about MORPHEUS, a 96-condition screen in which each condition integrates a mix of additives selected for their high occurrence in the Protein Data Bank, traditional cryoprotectant and buffer system. Recently, another paper presents the development related to MORPHEUS II, a follow-up to the original screen [Gorrec (2015). Acta Cryst. F71, 831-837; doi: 10.1107/S2053230X1500967X]. In this paper it is demonstrated that additives selected from the PDB that are under-represented in traditional screens can be combined to formulate suitable and useful conditions, not only for crystallization but the overall structure determination process.

Notably, the new screen includes protein stabilizers (e.g. sugars), heavy atoms to enable experimental phasing and glycerol-like polyols to alter the parameters of crystal cryoprotection. The suitability of the resulting novel conditions is shown by the crystallization of various protein samples produced at the Laboratory of Molecular Biology (LMB) and their efficiency is compared with commercially available conditions.