Minimal nucleotide duplex formation in water through enclathration in self-assembled hosts

Short nucleotide fragments such as mono- and dinucleotides are generally unable to form stable hydrogen-bonded base pairs or duplexes in water. Within the hydrophobic pockets of enzymes, however, even short fragments form stable duplexes to transmit genetic information. Here, we demonstrate the efficient formation of hydrogen-bonded base pairs from mononucleotides in water through enclathration in the hydrophobic cavities of self-assembled cages. Crystallographic studies and H-1- and N-15-NMR spectroscopy clearly reveals pair-selective recognition of mononucleotides and the selective formation of an anti-Hoogsteen-type base pair in the cage's cavity. Within an analogous expanded cage, dinucleotides are also found to form a stable duplex in water. These results emphasize how hydrogen-bonded base pairing is amplified in a local hydrophobic area isolated from aqueous solution.