1. a MRC Laboratory for Molecular Cell Biology , University College London , Gower St., London , WC1E 6BT , United Kingdom
2. b London Centre for Nanotechnology , University College London , Gordon St., London , WC1H 0AH , United Kingdom
3. c Department of Mathematics , University of Bristol , Bristol , BS8 1TW , United Kingdom
4. d Department of Physics and Syracuse Biomaterials Institute , Syracuse University , Syracuse , New York , 13244
5. e Department of Cell and Developmental Biology , University of California , San Diego, 9500 Gilman Drive, La Jolla , California , 92093
6. f MRC Laboratory for Molecular Cell Biology , University College London , Gower St., London , WC1E 6BT , United Kingdom E-mail: