The adsorption of amino acids and cations onto goethite: a prebiotic chemistry experiment

Few prebiotic chemistry experiments have assessed the adsorption of biomolecules by iron oxide-hydroxides. The present work investigated the effects of cations in artificial seawaters on the adsorption of Gly, alpha-Ala and beta-Ala onto goethite, and vice versa. Goethite served to concentrate K and Mg cations from solution; these effects could have played important roles in peptide nucleoside formation. Goethite showed low adsorption of Gly and alpha-Ala. On the other hand, beta-Ala (a non-protein amino acid) was highly adsorbed by goethite. Because Gly and alpha-Ala are the most common amino acids in living beings, and iron oxide-hydroxides are widespread on Earth, additional iron oxides should be studied. Increased ionic strength in artificial seawaters decreased the adsorption of amino acids by goethite. Because Na was highly abundant in the artificial seawater, it showed the highest effect on amino acid adsorption. beta-Ala increased the adsorption of K and Ca by goethite, this effect could have been important for peptide synthesis.