The first step in crystal structure determinations comprises the crystallization of the compound itself. To cover a large part of crystallization space, proper crystallization conditions are screened for using different techniques e.g. liquid-liquid diffusion, hanging- and sitting-drop vapor diffusion, microbatch,... depending on the nature of the compound.
Crystallization facilities and techniques are available for small (metal)-(in)organic molecules, as well as Mosquito nanodrop crystallization robotics for water-soluble nucleic acids, peptides and proteins, allowin the use of small sample volumes up to 50 nL drops (in collaboration with the Department of Biochemistry and microbiology, LProbe, prof. S. Savvides).
Once suitable hit conditions are found, the crystals are further optimized, and their quality checked under an Olympus SZ61-TR optical stereomicroscope, equipped with a polarizer/analyzer and tested for diffraction quality on an in-house diffractometer.
Diffraction data is collected on a four-circle Agilent Supernova diffractometer with dual wavelength (Cu and Mo) microfocus tube sources (40 W, 50 kV, 0.80 mA), Atlas CCD detector and Cryojet5 liquid nitrogen cooling device. This state-of-the-art equipment is available at the Department of Inorganic and Physical Chemistry and allows for the fast determination of the 3D molecular structure of the compound at the atomic level. The assignment of the absolute configuration of specific chiral atom sites can be determined, by using the anomalous signal between Friedel reflection pairs and calculation of refined Flack and Hooft parameters, together with their accuracy.
Several software packages are used in crystal structure determinations for the data collection, solving, refinement and structure analysis.
- Small molecules: CrysAlisPRO, SHELX, shelXle, Olex2, Mercury, Platon, WinGX,...
- Macromolecules: XDS, Mosflm, CCP4, Phenix, Coot, PyMOL,...
- Cambridge Structural Database CSD (Cambride Crystallographic Data Centre)
- Inorganic Crystal Structure Database ICSD (FIZ Karlsruhe)