1. Department of Cellular and Molecular Biophysics, Max Planck Institute of Biochemistry, D-82152 Martinsried, Germany
2. School of Life Sciences, Jiangsu Normal University, Shanghai Road 101, 221116 Xuzhou, P. R. China
3. Biosciences Division, University College London, Gower Street, WC1E 6BT London, U.K.