Isolation of compounds with affinity for copper from seawater using immobilized copper ion affinity chromatography

Abstract

Investigation of the use of immobilized metal ion affinity chromatography (IMAC) for isolation of compounds with affinity for copper from seawater was carried out. Samples from the Sargasso Sea, Chesapeake Bay and tributaries were analyzed using IMAC columns in a fast protein liquid chromatography (FPLC) system. Eluted compounds were detected by absorbance at 280 nm. Qualitatively, samples from various locations were similar, typically containing two resolved peaks with differing affinity for copper immobilized on the column. Ultraviolet irradiation of the seawater samples eliminated all of the high-affinity peak and most of the low-affinity peak, indicating that the peaks contained organic material. Analysis of constituents of these peaks in the estuarine water sample showed them both to contain protein and polysaccharide. Electrophoresis of IMAC fractions showed resolved components in the 14–42 kDa molecular weight range. In a depth profile to 1000 m in the Sargasso Sea the first (low-affinity) peak was found to be relatively invariant with depth whereas the second (high-affinity peak) exhibited a maximum at 60 m. The results show that IMAC is useful for concentration and partial purification of copper complexing organic compounds from seawater.