Helical structure of disodium 5'-guanosine monophosphate self-assembly in neutral solution.

Nucleic acid molecules (DNA and RNA) are formed by linking many different basic units known as nucleotides together via covalent phosphodiester bonds. Nucleic acid molecules often form helical structures known as B-DNA (right-handed), A-DNA/RNA (right-handed), and Z-DNA (left-handed). We have found that spontaneous self-assembly of just one nucleotide, guanosine 5'-monophosphate (5'-GMP), leads to formation of a right-handed helix in neutral solution. The linkage between individual 5'-GMP molecules along the helix is provided by hydrogen bonds, as opposed to the covalent phosphodiester bonds found in regular polynucleotides. The most surprising finding is that this right-handed 5'-GMP helix has alternating C2'-endo and C3'-endo sugar puckers along the helical strand, a situation only seen to date in left-handed Z-DNA. The self-organized structure of 5'-GMP provides a perfect condition for phosphodiester bond formation which may provide a clue for formation of RNA oligomers under prebiotic conditions. We anticipate that similar helical structures could exist in other nucleic acid systems.