Flash freezing of protein crystals: investigation of mosaic spread and diffraction limit with variation of cryoprotectant concentration

The effect of a cryoprotectant (glycerol) upon the mosaicity of flash-frozen T-state glycogen phosphorylase b crystals has been investigated. Glycerol concentration in a buffered solution was varied between 0 and 70% v/v. The results show that there is a well defined optimum in glycerol concentration giving lowest mosaicity, maximum resolution and no ice formation. The results also demonstrate how flash-freezing conditions can be systematically determined in-house using a minimum number of crystals and before using synchrotron time.