Cadmium-Sulfide Crystallites in Cd-(γEC)nG Peptide Complexes from Tomato

Hydroponically grown tomato plants (Lycopersicon esculentum P. Mill. cv Golden Boy) exposed to 100 micromolar cadmium sulfate produced metal-(gammaEC)(n)G peptide complexes containing acid-labile sulfur. The properties of the complexes resemble those of the cadmium-(gammaEC)(n)G peptide complexes from Schizosaccharomyces pombe and Candida glabrata known to contain a cadmium sulfide crystallite core. The crystallite is stabilized by a sheath of peptides of general structure (gammaGlu-Cys)(n)-Gly. The cadmium-peptide complexes of tomato contained predominantly peptides of n(3), n(4), and n(5). spectroscopic analyses indicated that the tomato cadmium-sulfide-peptide complex contained CdS crystallite core particles smaller than 2.0 nanometers in diameter.