1. B. Perman, Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637, USA.
2. V. Šrajer, Z. Ren, T.-y. Teng, C. Pradervand, K. Moffat, Department of Biochemistry and Molecular Biology and the Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637, USA.
3. T. Ursby, Molecular Biophysics, Chemical Center, Lund University, Post Office Box 124, S-221 00 Lund, Sweden.
4. D. Bourgeois, F. Schotte, M. Wulff, European Synchrotron Radiation Facility, 38043 Grenoble Cedex, France.
5. R. Kort and K. Hellingwerf, Laboratory for Microbiology, E. C. Slater Institute, 1018 WS Amsterdam, Netherlands.