Automated MAD and MIR structure solution

Obtaining an electron-density map from X-ray diffraction data can be diffic ult and time-consuming even after the data have been collected, largely bec ause MIR and MAD structure determinations currently require many subjective evaluations of the qualities of trial heavy-atom partial structures before a correct heavy-atom solution is obtained. A set of criteria for evaluatin g the quality of heavy-atom partial solutions in macromolecular crystallogr aphy have been developed. These have allowed the conversion of the crystal structure-solution process into an optimization problem and have allowed it s automation. The SOLVE software has been used to solve MAD data sets with as many as 52 selenium sites in the asymmetric unit. The automated structur e-solution process developed is a major step towards the fully automated st ructure-determination, model-building and procedure which is needed for gen omic scale determinations.