GRADE: Automatic generation of stereochemical restraints

GRADE from Global Phasing Ltd. is a ligand restraint generator whose main source of restraint information is the Cambridge Structural Database (CSD) of small-molecule crystal structures, queried using the MOGUL program developed by the CCDC. Where small-molecule information is lacking, Grade uses quantum chemical procedures to obtain the restraint values. The recommended procedure when dealing with a new structure is to supply the GRADE server with a .mol2 file containing 3D coordinates of all atoms as input. This way you can choose the atom names and sorting yourself. The grade-XXX.dfix file can be easily incorporated in the SHELX refinement via the '+filename' command, if the DFIX file is in the same folder as the SHELX RES and HKL file. Besides the output of restraints for non-hydrogen atoms, there is an option to get restraints for hydrogen atoms as well, which can be useful for neutron datasets. GRADE may be used free of charge irrespective of affiliation, no CSD license is required. The GRADE Web Server can be accessed here (information provided by Julian Holstein).