1. The Edinburgh Centre for Protein Technology, Joseph Black Building, West Mains Road, Edinburgh EH9 3JJ, Scotland, Department of Internal Medicine, Division of Rheumatology, Washington University School of Medicine, 660 South Euclid, Box 8045, Saint Louis, Missouri 63110, Institute of Cell and Molecular Biology, University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, Scotland, and Chemistry Department, Glasgow University, Glasgow, G12 8QQ, Scotland