Liquid crystal ordering and abiotic ligation of ultrashort DNA strands. Suggestions for a pre-RNA-world scenario.
We recently discovered that concentrated solutions of short oligonucleotides (down to 4 bases in length) spontaneously develop liquid crystal ordering. In such supramolecular assemblies, duplex-forming oligomers are held in average end-to-end contact to form chemically discontinuous but physically continuous double helices.
We found that this spontaneous order can serve as a mechanism for molecular selection and as a template to guide abiotic ligation toward the formation of long chains.
Specifically, we studied the influence of liquid crystal ordering of 5'-hydroxy-3'-phosphate DNA 12mers on the efficiency of non-enzymatic ligation reaction induced by water-soluble carbodiimide EDC as condensing agent. We find that the liquid crystal ordering dramatically enhances the ligation efficacy, yielding DNA chains having lengths of hundreds of bases and thereby enhancing its own phase stability.
These results suggest that the spontaneous ordering so easily observed in solutions of oligonucleotides may have been the key feature that enabled the emerging of nucleic acids from the primordial molecular noise.