"Testing Models of Peptide and Pre-RNA Assembly on Clay Minerals and in the Solid Phase"
The modern theory of chemical evolution is based on the assumption that on a primitive earth a mixture of simple chemicals assembled into more complex molecular systems, from which, eventually came the first functioning cell(s). In this extremely complicated series of transformations several key transitions must be contemplated. Two areas which present particular difficulties for the theory is the origin of homochirality and the polymerization of simple monomers into information rich networks, i.e. amino acids into proteins and a mixture of purines/pyrimidines/sugars into nucleic acids. Although many models have been advanced to explain these critical transformations, very little experimental evidence has been provided to support the claims. It will be the aim of this presentation to examine certain lines of evidence regarding the prebiotic simulations for the formation of simple peptides from amino acids and pre RNA molecules from heterocyclic bases and the appropriate connecting backbone. The primary focus'will be on chemical processes induced over inorganic clay mineral surfaces and solid phase mixtures as these are generally the most accepted mechanisms to date. Further, the dilemma of which came first, homochirality or life will be brought into the discussion since all naturally occurring peptides and nucleic acids are homochiral. Results of experiments designed to examine the stereochemical stability of simple peptides and homochiral RNA precursors under the major types of prebiotic reaction conditions will be reported. If stereochemical information is retained, then the simulation would stand as valid. Contrariwise, if stereochemical information is lost over measurable periods of time, then alternative scenarios explaining the formation of the molecular systems will have to be considered.