Chemical forms of technetium in tomato plants; TcO 4−, Tc–cysteine, Tc–glutathione and Tc–proteins

Abstract

The rapid accumulation of Tc, originating from nuclear power generation, in plants and the phytotoxicity at low Tc levels suggest an interaction between Tc and proteins. In the present study, different chemical forms of Tc in tomato plants were identified using an approach explicitly designed to prevent artefacts. After precipitation of Tc–proteins (80% ammonium sulphate), TcO 4 −, Tc–cysteine, and Tc–glutathione were determined, using reversed-phase ion-pair chromatography. A vast range of Tc–proteins was detected using a gradient of ammonium sulphate precipitation or hydrophobic interaction chromatography. The hypothesis that Tc, as an S-analogue, is organo-metallically incorporated into organic substances appears to be rather unlikely, because all reduced Tc in the leaves was susceptible to ligand-exchange with 2-mercaptoethanol. A ligand exchange route for reduced Tc from proteins to cysteine and glutathione in the leaves was suggested, using Tc species ratios and mathematical modelling.