INTEGRATED BEAMLINE CONTROL FOR PROTEIN CRYSTALLOGRAPHY. Robert M. Sweet and John M. Skinner, Biology Department, Brookhaven National Laboratory, Upton, NY 11973.

We have constructed a Graphical User Interface-driven software system for control of beamline X12-C at the NSLS. The beamline is equipped with a hybrid diffractometer, consisting of an Enraf Nonius CAD4-style diffractometer, carrying a 300mm-diameter MAR Research imaging-plate detector on its I arm.

The beamline itself is equipped with fairly standard apparatus - slits, monochromator, mirror, counters, and lift table for alignment of the diffractometer to the x-ray beam. Several programs run as independent images to perform various functions: diffractometer control, MAR scanner control, image transformation, and stepping-motor and counter control. These programs are controlled by a graphical-user-interface program that integrates their functions and provides communication among them.

The system contains the full functionality expected of any diffraction system (based on Pflugrath and Messerschmidt's MADNES), and flexible control of the beamline too. One can do nearly automatic alignment of the diffractometer to the x-ray beam. A recent innovation is the automatic collection of MAD data - with a single set of instructions the system will measure multiple sweeps of data, perhaps including Bijvoet-pair data measured by the Friedel-Flip method. At each wavelength change, the absorption spectrum of the anomalous scatterer is measured automatically and analyzed to select precisely the best wavelength before the start of each sweep. A second innovation allows monitoring of the x-ray beam in the synchrotron, a pause for a refilling of the ring, and a realignment and restart after the beam has been restored and is stable

This work was supported by the Office of Health and Environmental Research of the United States Department of Energy and by the National Science Foundation.