Surface charges and interfaces: Implications for mineral roles in prebiotic chemistry

There exists an extensive literature on the possible roles of minerals in t he prebiotic stages of the chemical evolution of life (Bernal 1951, Cairns- Smith 1987, Wachtershauser 1992, Vieyra er al. 1995, Tessis et al. 1999, se e Lahav (1994) for. a review). Among the original proposals, minerals have been considered in: (a) processes that would discriminate molecular chirali ty; (b) condensation reactions of biomolecular precursors; (c) prebiotic ca talysis; (d) biochemical templates; and (e) autocatalytic metabolism. In th is communication it is emphasized the complex properties of both surface re actions and interfaces between minerals and aqueous solutions simulating Ar chean scenarios. The propel-ties of pyrite surface net charge and of its in terface with a solution simulating primitive seawater are discussed and the ir implications to the autocatalytic model (Wachtershauser 1988a 1992) are presented in order to demonstrate their relevance. The proposed roles of ir on-sulfide minerals (mainly pyrite) as physical support for primitive bidim ensional metabolism and chiral discriminator (Wachtershauser 1988a, Huber & Wachtershauser 1998) are revised. It is shown that: (a) the net surface ch arge can be modulated by the: pyrite-aqueous solution interface; (b) mononu cleotides attachment to pyrite require a cationic bridge; and (c) direct ab sorption of acetate - a molecule proposed as carbon source in primitive aqu eous environments - also modulates the interface properties and would have masked pyrite's bulk structure. These results indicate that physicochemical changes of mineral surfaces - caused by environments simulating Archean aq ueous scenarios - should be taken into account in the proposals of mineral prebiotic rules.