INVESTIGATION OF THE METAL ALGAE BINDING-SITE WITH CD-113 NUCLEAR-MAGNETIC-RESONANCE

Metal-algae interactions in a unialgal culture (Stichococcus bacillaris) are examined by 113Cd nuclear magnetic resonance (NMR) spectroscopy. In addition to a peak attributed to cadmium in solution, a second broad resonance is assigned to cadmium binding with the algal cell wall. Studies of competitive uptake with other metals permit an affinity ranking assigned as Cu, Fe > Cd, Co, Na. pH studies indicate that although the presence of protons in the solution does not chemically alter the nature of the binding sites, the excess protons will directly replace the bound Cd. An NMR chemical shift of −10 to −18 ppm for the bound cadmium indicates the functional group responsible for metal uptake is most likely a carboxylic group. The chemical shift of the resonance also suggests the carboxyl groups involved in metal adsorption may possess larger chain lengths and perhaps multiple carboxyl groups per chain. © 1990, American Chemical Society. All rights reserved.