This project involves experimental studies of possible mechanisms for the geochemical origin of RNA precursors. Derivatives of hydrogen cyanide form the bases of RNA, whose origin is extrapolated to -4.3 billion years. Several investigations have shown pathways for purine and pyrimidine synthesis, which are viable, but only at relatively high reactant concentration in aqueous solution. A crucial problem in applying these results to prebiotic molecular evolution concerns the selective concentration of the reactants from the dilute solution in which they probably existed. High concentrations must have been consistly maintained in order to permit reactions leading to cyanide oligomers and to the ordered heteropolymers that would have served as forerunners for RNA. Current experiments indicate that common transition element minerals under appropriate environmental modeling conditions are capable of photosynthesis of carboxylates, sorption of cyanide against large concentration gradients, and immobilization of the polymeric reaction products. The proposed studies involve concentration of cyanide from extreme dilution by sorption and intercalation in surface active transition element minerals, followed by spontaneous or photochemically induced oligomerization and condensation reactions to form potential mineral-organic hybrid precursors of the genome.
