Fig. 5 HPLC-ESI-MS(TOF) analysis of PC and Hg–biothiol complexes in Arabidopsis Col-0 xylem sap. (a)Chromatographic profile of reduced PC2, oxidized (PC2oxd), and HgPC2 detected in the xylem samples (in negative mode). (b)[HgPC2+H]+ Molecular ion distribution (in m/z ) compared with the theoretical one and a standard complex, prepared by mixing PC2:HgCl2 at 10:10 µM ratio (in positive mode). (c) and (d) MS2 and MS3 fragmentation profiles of [HgPC2+H]+, compared to those obtained using a standard PC2:HgCl2mixture (insets), all in positive mode.