Bonding states of palladium in phytosystems: First results for endive

The binding of palladium to organic ligands was studied in leaves from contaminated endive. The palladium-treated plants contained 8.7 ng Pd/g referring to wet weight. After a cell breakdown in buffer the resulting homogenate was separated into supernatant and pellet by centrifugation and the distribution of palladium was determined. The liquid fraction contained 40% of the total palladium and was further separated by ultrafiltration. This technique revealed that 23% of total palladium was present as high molecular weight species (>10 kDa). After concentration, the high molecular weight fraction was further investigated by gel permeation chromatography (GPC). By this method only one elution range for palladium was observed. The size range of the GPC used was about 20-8000 kDa for globular proteins. The palladium elution maximum was detected in the range of about 160 kDa. The determinations of palladium were performed by total-reflection X-ray fluorescence after palladium separation and preconcentration.