[1] Oxford Centre for Molecular Sciences, Central Chemistry Laboratory, South Parks Road, OX1 3QH Oxford, United Kingdom
[2] Dept. of Chem. and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, MA 02138
[3] Laboratoire de Chimie Biophysique, ISIS, Université Louis Pasteur, 4 rue Biaise Pascal, 67000 Strasbourg, France