Book of Abstracts: Albany 2007
June 19-23 2007
On the Route from Formamide to Informational Polymers
The simplest molecules grouping the four most common elements of the universe H, C, O, and N (with the exception of the biologically inert He) are isocyanate HNCO and formamide H2NCOH. Reasons for the availability of formamide on prebiotic Earth are presented. We review evidence showing that formamide in the presence of largely available catalysts and by moderate heating yields the complete set of nucleic bases necessary for the formation of nucleic acids and favors the formation of acyclonucleosides. In the presence of formamide, crystal phosphate minerals may act as phosphate donors to nucleosides yielding 5?, 3?, 3?:5?- and 2?:3?- cyclic phosphorylated forms.
Data will be presented on the phosphorylation properties of a large panel of minerals. Based on their behavior in the formamide-driven nucleoside phosphorylation reaction these minerals can be: (i) inactive; (ii) low-level phosphorylating agents; and (iii) active phosphorylating agents. Instances were detected in which phosphorylation occurs onto the mineral surface, followed by release of the phosphorylated compounds.
Thus, activated nucleic monomers can form in a liquid non-aqueous environment in conditions compatible with the thermodynamics of polymerization, thus providing a solution to the standard-state Gibbs free energy change (ΔG°?) problem, the major obstacle for polymerizations in liquid phase in plausible prebiotic scenarios.
In a larger perspective, physico-chemical conditions were determined in which formamide favors the stability of the phosphoester bonds in nucleic polymers relative to that of the same bonds in monomers. Starting from a formamide-rich environment subject only to the laws of chemistry, a hypothesis is thus outlined sketching the passage towards an aqueous world in which Darwinian rules began to apply.
References and Footnotes
Ernesto Di Mauro
Dipartimento di Genetica e Biologia Molecolare