Cd2+ and Pb2+ complexation by glutathione and the phytochelatins.

摘要: Abstract Phytochelatins or PCn, (γGlu-Cys) n -Gly, and their glutathione (GSH) precursor are thiol-rich peptides that play an important role in heavy metal detoxification plants microorganisms. Complex formation between Cd 2+ Pb GSH PCn (n = 2, 4 6) investigated by microcalorimetry, absorption spectrophotometry T-jump kinetics. with is exothermic, induces ligand charge transfer bands UV spectral range, which implies the of a coordination bond thiol groups phytochelatins. Absorption spectra microcalorimetry experiments allow determination affinity constants stoichiometry complexes. We show three interact to form 1:1 2:1 M:L complexes, similar (log K 11 ∼4.6, log 21 ∼11.4). These affinities independent number thiols are, moreover, lower than those determined for complex . On other hand, , PC2-Cd, PC2-Cd 2 (PC2) 3 -Cd PC4-Cd, PC4-Cd PC6-Cd, (PC6) PC6-Cd complexes detected. Furthermore, most stable: constant ∼7.5). Kinetic studies indicate occurs ms range; direct rate k obs  = (6.8 ± 0.3) 10 6  M −1  s reverse −  = 340 ± 210 s Thus, when encapsulated silica matrix, can be good candidates detection.