[1] Univ Oxford, Dept Chem, Oxford OX1 3QZ, England
[2] Free Univ Berlin, Inst Chem & Biochem, D-14195 Berlin, Germany
[3] Max Planck Gesell, Fritz Haber Inst, Dept Mol Phys, D-14195 Berlin, Germany
[4] Univ Oxford, Dept Biochem, Oxford Glycobiol Inst, Oxford OX1 3QU, England
[5] Macquarie Univ, Biomol Frontiers Res Ctr, Sydney, NSW 2109, Australia