TOWARDS THE FULL AUTOMATION OF MAP INTERPRETATION Thomas Oldfield, Department of Chemistry, University of York, Heslington, York, Y01 5DD UK

Recent developments in recombinant DNA techniques, crystallisation protocols, X-ray data collection techniques and devices, and computing have led to a substantial increase in the speed and number of protein structure determinations in modern crystallographic laboratories. However, there still remains a number of key stages in the crystallographic process which limit the rate of structure determination. One of these is fitting electron density maps, either in the initial stages of tracing a chain to a new map, or in the manual rebuilding during refinement. This is a particularly onerous task, requiring many days and often weeks of working at a graphics terminal with maps and model.

The electron density applications available within the new version of QUANTA ( QUANTA 96 ), represent novel and effective tools for speeding up this process. The various modules ( X-AutoFit, X-Ligand, X-Solvate and X-Build ) have been developed over the past year in close collaboration with the large number of crystallographers working on projects in the Protein Group at York. Crucially, these new tools are easy to learn and natural to use, providing up to a 10 fold reduction in the time spent at the graphics terminal.

During my presentation, I will show how the semi-automated tools within this application can be used for the interpretation of maps calculated with experimental phase information. I will also present methods which go some way towards the automatic interpretation of electron density, and the limitations of these methods as a function of resolution and quality of maps.