Adsorption and Catalysis of Nucleotide Hydrolysis by Pyrite in Media Simulating Primeval Aqueous Environments

Abstract

Metal sulfides have been proposed as physical support for primitive bidimensional metabolism and chiral discriminators. There are controversial data about the possibly coupling between the exergonic pyrite syntheses and the endergonic amino acids syntheses in pyrite pulled metabolic-like processes. However, a role in adsorption and catalysis involving biomonomers — such as nucleotides — cannot be ruled out in an especial aqueous scenario. In an aqueous environment with a vast reservoir of reducing power in the form of, especially, iron (II) and sulfide within and beneath the crust. Our hypothesis is that ancient minerals such as pyrite could have played a role in concentrating mononucleotides and in determining their catalytic routes in later periods, when polynucleotides appeared and evolved (Tessis et al., 1999). Pyrite — as well as other sulfides — could have participated in nucleotide adsorption and in primitive phosphoryl transfer reactions in the less drastic conditions that prevail away from the hot hydrothermal vents, the big sources of starting molecules. In this presentation, we shall briefly comment about our results on the following themes: 1) Adsorption of mononucleotides (AMP and ADP) onto untreated and acetate-treated samples of pyrite in which soluble Fe³⁺ ions were removed; 2) The influence — on nucleotide adsorption — of the previous adsorption onto the crystal of an oxo acid that could have appeared near the mineral and modified its surface properties (acetate can be formed onto the surface of mixed iron nickel sulfides at high temperature and pressure [Huber and Wächtershäuser, 1997]); 3) The role of the interface. In some models, the two-dimensional system represented by a mineral surface would be in a seawater environment having a passive role. The actual conditions prevailing when sulfur materials are in contact with salt solutions are quite complex. The very reactive iron-sulfide immersed in a solution resembling a primitive ocean generates a continuously changing interface with ionic gradients and formation of different oxide layers; 4) Hydrolysis of ATP adsorbed onto pyrite.