[1] Univ Sheffield, Dept Mol Biol & Biotechnol, Sheffield S10 2TN, S Yorkshire, England
[2] Kings Coll London, Dept Pharm, Pharmaceut Opt Spect Ctr, London WC2R 2LS, England
[3] Inst Canc Res, Chester Beatty Labs, Sect Struct Biol, London SW3 6JB, England
[4] Kings Coll London, Div Life Sci, London W8 7AH, England