Direct Observation of the Double‐Stranded DNA Formation through Metal Ion‐Mediated Base Pairing in the Nanoscale Structure.

This work demonstrates single‐molecule imaging of metal‐ion induced double‐stranded DNA formation in DNA nanostructures. The formation of the metal ion‐mediated base pairing in a DNA origami frame was examined using C‐Ag‐C and T‐Hg‐T metallo‐base pairs. The target DNA strands containing consecutive C or T were incorporated into the DNA frame, and the binding was controlled by the addition of metal ions. Double‐stranded DNA formation was monitored by observing the structural changes in the incorporated DNA strands using high‐speed atomic force microscopy (AFM). Using the T‐Hg‐T base pair, the dynamic formation of unique dsDNA and its dissociation were observed. The formation of an unusual shape of dsDNA with consecutive T‐Hg‐T base pairs was visualized in the designed nanoscale structure. Single‐molecule imaging of the metal‐ion‐mediated formation of dsDNA in a DNA frame was demonstrated. By using two types of metallo‐base pairs C‐Ag‐C and T‐Hg‐T, formation of dsDNA from two consecutive C and T strands in the presence of metal ions was characterized. The dynamic formation of dsDNA using T‐Hg‐T was directly observed using high‐speed atomic force microscopy. [ABSTRACT FROM AUTHOR]