[1] European Bioinformat Inst, European Mol Biol Lab, Welcome Trust, Hinxton CB10 1SD, Cambs, England
[2] Metabolomx, Mountain View, CA 94043 USA
[3] Univ Cambridge, Dept Biochem, Cambridge CB2 1GA, England
[4] Univ Cambridge, Cambridge Syst Biol Ctr, Cambridge CB2 1GA, England