[1] Pfizer Global Res & Dev, Dept Med Informat Struct & Design, Sandwich Labs, Sandwich CT13 9NJ, Kent, England
[2] Astex Technol Ltd, Cambridge CB4 0QA, England
[3] Univ Leicester, Dept Chem, Leicester LE1 7RH, Leics, England
[4] Univ Leicester, Dept Biochem, Leicester LE1 7RH, Leics, England