Dissolved copper in surface seawater in many locations exists primarily in complexes with strong organic ligands, which are distinguished by their complexing strengths. However, these ligands have never been isolated and characterized; thus, almost nothing is known about their chemical nature. Isolation and characterization of these ligands is extremely important to our understanding of the biogeochemical cycling of copper and the ligands themselves, and perhaps that of other metals which may be similarly complexed. Recently, immobilized metal (Cu2+) affinity chromatography (IMAC) has been used to purify extracellular copper- binding proteins produced by marine bacteria, and also to isolate and partially characterize organic compounds with affinity for copper from estuarine, coastal, and open ocean waters. IMAC- isolated ligands have depth distributions similar to those of ligands that strongly complex Cu in the Atlantic and Pacific. This pilot project will determine whether IMAC, using either established or modified protocols, can isolate these ligands, ligands detected in seawater by differential pulse anodic stripping voltammetry (DPASV) and ligand competition/differential pulse cathodic stripping voltammetry (LC/DPCSV). The appropriate IMAC protocol will then be used in conjunction with DPASV and LC/DPCSV to characterize the ligands in coastal surface seawater with respect to: their concentrations, conditional stability constants, relative proportions of protein and polysaccharide comprising them, and molecular weight.
