Isolation and partial characterization of dissolved copper-complexing ligands in streamwaters

We have separated two groups of copper-complexing ligands (the weak and str ong ligands) from streamwaters in the Lake Biwa watershed by modified immob ilized metal ion affinity chromatography (IMAC). The weak ligands were abou t 0.54-1.21% of the total dissolved organic matter (DOM), as determined by UV absorbance, and the strong ligands were about 0.06-0.21%. The results sh ow that the stronger ligands were retained longer on the IMAC column, elute d later, and were accompanied by shorter wavelength UV absorbers, fluoresce nce maxima patterns with shorter wavelength excitation, and relatively "fre sher" organic matter. The weak ligands with logK ' (CuL) values of 6.6-7.7 had predominant humic-like fluorescence and may have been considerably degr aded, while stronger ligands with logK ' (CuL)values of 8.9-9.3 had only pr otein-like fluorescence and were relatively newly produced, labile material , as indicated from their amino acid composition. The protein-like fluoresc ence was mainly due to aromatic tryptophan probably bound to proteins or pe ptides. The results presented here have significant implications regarding the possible sources and biogeochemical role of organic ligands in aquatic environments.