1H NMR Studies of Alginate Interactions with Amino Acids

The interactions between alginate and the amino acids, histidine, lysine, phenylalanine, and alanine, were studied by Proton Nuclear Magnetic Resonance. The characterization of the amino acids interaction with alginate was performed by 1D and 2D-NOESY experiments. Measurements of 1 H NMR nonselective and selective relaxation rates in the absence and presence of alginate were used to calculate interaction constants between each amino acid and alginate. The interaction constants were found to be related to the hydrophobicity of the different amino acid side-chains. The interaction constant between phenylalanine and Ca 2+ crosslinked alginate was also determined. There was no apparent differences observed in the crosslinked and the solution amino acid-alginate interactions. On the basis of the experimental results obtained, a model of the interaction between amino acids and alginate was proposed.