EXPLORING THE ROLE OF LIQUID CRYSTAL ORDERING OF DNA OLIGOMERS IN THE PREBIOTIC SYNTHESIS OF NUCLEIC ACIDS

The work in this thesis has been devoted to study the self-assembly of DNA oligomers in light of their possible relevance in the context of the formation of longer chains of nucleic acids in the prebiotic world. This conjecture is based on previous evidence of hierarchical self-assembly of short oligonucleotides in solution that provides mechanisms of self-selection. In such self-assembled structures, the 3’ and 5’ terminals are held in close contact, a condition that could act as a spontaneous template for the elongation of the chains in conditions favoring their chemical ligation. The work here described was aimed at testing this notion by various investigations targeting what appeared to be the most critical issues in this context. Accordingly, I acted in three main directions. First I investigated if LC ordering, and hence ligation templating, emerges even in solutions of oligomers having sequences chosen at random, and I determined a new extended phase diagram which includes the degree of randomness. Second, I determined what is the minimum oligomer length which enables the formation of LC phases and I found that LC phases can be found in solution of oligomers as short as 4-bases, and even with randomly chosed sequences. This last result was actually quite suprising and indicates the existence of a new regime for the self-assembly of ultra-short DNA chains. Third, I explored the influence of LC ordering of short DNA oligomers on non-enzymatic ligation reaction favored by the presence of a water-soluble condensing agent. I found a good yield for the polymerization of DNA oligomers both in isotropic than in LC phases, and polymerized chains up to 12 times longer than the initial length. I believe the work described in this thesis strengthens the notion that self-assembly of nucleic acids could indeed have been the key factor promoting the formation of long chains. These results shad a new light on the most obscure among the processes that enabled the emergence of life on the early Earth.