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E. Di Mauro - Spontaneous formation and evolution of informational nucleic polymers
- Do these differential conditions affect sequence evolution?
Conditions were determined for the polymerization
of prebiotically formed monomers into oligomers
and increasingly complex informational structures.
Three levels of abiotic polymerization were attained:
i) from 2’-3’ cyclic and 3’-5’ cyclic nucleotides:
oligomerizations up to 9-mers;
ii) from 15-nucleotides-long oligomers: 3’-5’ phosphodiester
bonds reshuffling and oligomers formation,
resulting in chain elongation up to 25 mers;
iii) form 15-nucleotides-long oligomers: multimerization
to dimers, trimers and higher forms.
These results provide the proof-of-principle that abiotic
polymerization are obtained spontaneously. In
addition, a set of conditions are established which
may provide the test systems for the analysis of stability
of genetic information in acellular, space-wise
conditions.
A large panel of new catalysts was tested in synthetic
reactions from formamide: basalts, sulphurcontaining
minerals, zircons. The results obtained
are instrumental to the formulation of a chemical
theory of the origin of informational polymers and
for the search of life in non-terrean environments.
Syntheses have been performed in the presence of
FeS, Pyrrhotine, Fe (1-x) S, FeS 2 , Pyrite FeS 2 ,
Chalcopyrite FeCuS 2 , Bornite, FeCu 5 S 4 ,
Tetrahedrite, (Fe,Cu,Sb)S, Covellite, CuS,
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Covellite:pyrite (2:1), Covellite:pyrite (3:1),
Covellite:pyrite (4:1), starting from the substrate formamide.
Quite interestingly the products obtained
are precursors of nucleic acids and related compounds,
namely purine, (1H)-pyrimidinone, isocytosine,
adenine, 2-aminopurine, carbodiimide, urea,
oxalic acid. The stability properties of nucleic acids
in the presence of these minerals were analyzed. The
results clearly show that iron-based catalysts have
strongly degradative capacity and that the origin of
informational polymers with these catalysts only can
be based upon the evolution of specific protective
mechanisms of the polymers (“encapsulation” in
lipids, interaction in the clays, etc.). The results
obtained with zirconium-based catalysts are in
preparation.
Selected publications
Ciciriello F, Costanzo G, Pino S, Crestini C,
Saladino R, Di Mauro E. Molecular complexity
favors the evolution of ribopolymers. Biochemistry
2008, 47:2732-42.
Pino S, Ciciriello F, Costanzo G, Di Mauro E.
Nonenzymatic RNA ligation in water. J Biol Chem.
2008, 283:36494-503.
Saladino R, Neri V, Crestini C, Costanzo G,
Graciotti M, Di Mauro E. Synthesis and degradation
of nucleic acid components by formamide and iron
sulphur minerals. J Am Chem Soc. 2008, 130:15512-8.