Pyrite and phosphate in anoxia and an origin-of-life hypothesis

The metal-sulfide pyrite (FeS2) plays a key role in the elaborate origin-of-life hypothesis presented by Wächtershäuser [G. Wächtershäuser, Proc. Natl. Acad. Sci. USA 87 (1990) 200–204]. It is envisaged that the in-situ formed, positively charged pyrite was electrostatically concentrating the de novo synthesized prebiotic anionic organic molecules in statu nascendi. Here we show that anionic phosphate and phosphorylated organic molecules (5′-Adenosine Mono Phosphate and Phosphoglyceric Acid) interact with pyrite, regardless of whether the overall surface charge is positive or negative. We demonstrate that aqueous Fe2+ metal ion, H2S and S2O2−3 influence the interaction of phosphate with pyrite. Phosphate itself controls the interaction of Adenosine (Ade) and 5′-AMP with pyrite. 5′-AMP interacts via its phosphate functional group with pyrite surfaces. The reported experiments illustrate the intermediary role of phosphate between pyrite mineral surfaces and aqueous organic molecules. We suggest here that, on a prebiotic Earth, phosphate could have been concentrated on metal-sulfide minerals, which in turn were selectively concentrating organic molecules, favoring phosphorylated compounds.