Modulation of Adenosine 5′-Monophosphate Adsorption Onto Aqueous Resident Pyrite: Potential Mechanisms for Prebiotic Reactions

The adsorption of adenosine 5-monophosphate (5-AMP) ontopyrite (FeS₂) and its modulation by acetate, an organic precursor of complex metabolic pathways, was studied in aqueousmedia that simulate primitive environments. 5-AMP adsorptionrequires divalent cations, indicating that a cationic bridge mediates its attachment to negatively charged sites of the mineral surface. The isotherm of 5-AMP adsorption exhibits a strong cooperative effect at low nucleotide concentrations inacetate-rich medium, whereas high levels of adsorption were only found at high nucleotide concentrations in a model of primitive seawater (acetate free). The modulating role of acetate is also evidenced in the presence of high dipolar moment molecules: dimethyl sulfoxide (Me₂SO) and dimethylformamide (DMF) strongly inhibit 5-AMP adsorption in acetate-rich media, whereas no effect of DMF was found in artificial seawater. The observation that exogenous divalentcations are not needed for acetate attachment onto FeS₂ reveals that organic acids can interact with the Fe²⁺ atoms in the mineral surface. All considered, the results showthat complex and flexible iron-sulfide/biomonomers interactionscan be modulated by molecules that accumulate in the interfacelayer.