1. Key Laboratory of Combinatorial Biosynthesis and Drug Discovery (Ministry of Education)School of Pharmaceutical SciencesWuhan University 185 East Lake Road Wuhan 430071 P. R. China
2. Division of Structural BiologyWellcome Centre for Human Genetics Roosevelt Drive Oxford OX3 7BN UK
3. The Research Complex at Harwell Harwell Campus OX11 0FA UK
4. The Rosalind Franklin Institute Harwell Campus OX11 0FA UK