N2'→p3' Phosphoramidate Glycerol Nucleic Acid As A Potential Alternativegenetic System

摘要

Glycerol nucleic acid (GNA), which is based upon an acyclic, three-carbon backbone (Figure 1A), is a promising starting point for the construction of an artificial genetic system owing to its ability to form stable, antiparallel duplexes.As proposed by Orge we imagine that a nonenzymatic, template-directed polymerization process mediated replication during the evolution of early genetic systems,in place of enzymatic replication as in the modern genetic system. To recapitulate this process, our group has focused on the chemistry of polymerization facilitated by an imidazole-activated phosphate group and an amino group as the nucleophile (Figure IB and 1C, highlighted in red). This approach requires the newly synthesized strand with N→P phosphoramidate linkages to form stable, Watson-Crick base pairs with the template strand. The base-pairing properties of the GNA analogue with N2'→P3' phosphoramidate linkages (npGNA, Figure 1A) have not been fully explored. In this study, we demonstrate that npGNA can form stable duplexes with itself and with GNA. We also show that GNA oligonucleotides containing N2'→P3' phosphoramidate linkages can be assembled via a nonenzymatic, template-directed ligation of 3'-imidazole-activated-2'-amino GNA dinucleotides (Figure 1C). These results suggest that npGNA is a potential candidate for a self-replicating system based on phosphoramidate linkages.