PROTEIN CRYSTAL PERFECTION AND THE CRYSTAL GROWTH PROCESS. E.H. Snell, J.R. Helliwell, A. Cassetta, T.J. Boggon, Chemistry Department, University of Manchester, Manchester, M13 9PL. UK, N.E. Chayen Biophysics Section, The Blackett Laboratory, Imperial College, London SW7 2BZ. UK, E. Weckert, K. Holzer, K. Schroer, Institut fur Kristallographie, University of Karlsruhe (TH), Kaiserstrasse 12, Postfach, 6980 D-76128, Karlsruhe. Germany, V. Stojanoff, D.P. Siddons, NSLS, Brookhaven National Laboratory, Upton, NY 11973. USA

A program of work is underway involving the improved characterisation of protein crystals, grown in microgravity and on earth, and the monitoring of the process of crystal growth. Characterisation techniques include detailed mosaicity and topography measurements, which has involved use of SRS, ESRF and NSLS synchrotron X-ray facilities. Monitoring of the crystal growth process is being done via CCD video and interferometry (the latter to follow refractive index changes). Assessmant of microgravity versus earth based methods is made possible by use of ESA's APCF flown on the NASA Space Shuttle. Improved quality of lysozyme crystals grown in microgravity (by dialysis) has been demonstrated. Apocryustacyanin C1 (grown by vapour diffusion) shows an improvement but not as marked. Comparison of methods of crystal growth, including CCD video monitoring of motion of crystals suggests that dialysis methods are superior to vapour diffusion for microgravity crystal growth. A depletion zone around each growing apocrustacyanin C1 crystal is seen in the video data. The X-ray diffraction characterisation can be summarised via plots of mosaicity versus peak reflection height which allow sensitive diagnosis of improved perfection. Correlation of topographic mosaic block size can be made with the rocking curves of the microgravity crystals. The combination of diagnostic techniques and perfection anlayses is giving better insights into the optimum conditions for protein crystallization for the realisation of the best signal- to-noise ratio in X-ray reflection intensity measurements.