[1] Univ Leeds, Sch Phys & Astron, Inst Mol Biophys, Leeds LS2 9JT, W Yorkshire, England
[2] Univ Leeds, Sch Biochem & Microbiol, Leeds LS2 9JT, W Yorkshire, England
[3] Univ Leeds, Sch Phys & Astron, Astbury Ctr Struct Mol Biol, Leeds LS2 9JT, W Yorkshire, England