Binding of Hg~(2+) with Phytochelatins: Study by Differential Pulse Voltammetry on Rotating Au-Disk Electrode, Electrospray lonization Mass-Spectrometry, and Isothermal Titration Calorimetry

摘要

The binding of Hg~(2+) with synthetic phytochelatins ((γ-Glu-Cys)_n-Gly, PC_n, n = 2,3,4) was investigated by a recently proposed electroanalyticat method, using differential pulse voltammetry on the rotating Au-disk electrode, Electrospray ionization mass-spectrometry (ESI-MS) and isothermal titration calorimetry (ITC). ESI-MS experiments provided the exact stoichiometries of the complexes formed at different PC_n/Hg~(2+) ratios. Voltammetry provided more detailed information on the complexation processes through the use of multivariate curve resolution by alternating least squares of the data matrix obtained from titrations with fine increments of metal or ligand. The system Hg~(2+)-GSH-PC_2 was investigated by voltammetry in order to obtain an estimation of the Hg~(2+) behavior in the presence of two related ligands. The additional assessment of the stability of Hg~(2+)-PC_n complexes was achieved through ITC by using the therapeutic chelator sodium 2,3-dimercaptopropanesulfate (DMPS) over Hg~(2+)-PC_n systems. The stability of various Hg~(2+)-PC_n complexes and the ability of DMPS to replace PC_n from these complexes were examined.