7. Validation and quality control of structures

One of the final steps in the process of determining a 3D structure is the validation and quality control of the structure. A crystallographic structure is the result of a number of steps, involving interpretations (which may be subjective) of the data and a structure determination protocol (choice of programs and parameters used by these programs). This structure may therefore contain errors (local or global, corresponding to a partially false or incomplete model) which may result from poor data quality, unsuitability of the programs used, or perhaps the relative inexperience of the scientists who built and refined this structure. The aim of this validation and quality control stage is to minimize these errors and provide the three-dimensional structure which, given the current state of the methods and techniques used, is in best agreement with the experimental data. Validation and quality...