X-ray analysis of protein crystals with thin-plate morphology

A case study on quasi two-dimensional crystals of the serine kinase domain of the giant muscle protein titin is presented. These crystals were obtained from several precipitating agents. However, under all conditions their growth in the third dimension was inhibited resulting in very thin plates, hardly visible under the microscope. Here a number of aspects that have been essential for highresolution data collection from these crystals are described: (i) improvement of the crystals by ®ne tuning their growth, namely by the addition of organic solvents, the application of macroseeding, and the reduction of vapour diffusion in the crystal drop vials using oil mixtures over the reservoir solutions; (ii) cryomounting techniques preventing mechanical stress; and (iii) optimizing the use of synchrotron radiation.