pH-Stimulated Reconfiguration and Structural Isomerization of Origami Dimer and Trimer Systems

Reversible pH-responsive dimer or trimer origami structures ale assembled by bridging origami frames with pH-responsive units. The cyclic pH-stimulated separation and reassembly of dimer origami structures is demonstrated using i-motif or Hoogsteen-type (C-G center dot C+ or T-A center dot T) interactions. The,duplex-bridged dimer T-1-T-2 is separated by the pH-induced formation of an i-motif structure (pH = 4.5), and the dieter is reassembled at pH = 7.0. The duplex-bridged dimer, T-3-T-4, is separated at pH = 4.5 through the formation of C-G center dot C+ triplex structures and is reassembled to the dimer at pH = 7.0. Similarly, the T-A center dot T triplex-bridged T-5-T-6, is separated at pH = 9.5 and is reassembled at neutral pH. Finally, a trimer, T-3-T-7-T-6, that includes C-G. C+ and T-A center dot T pH-responsive bridges reveals pH-programmed Cleavage to selectively yield the diners T-3-T-7 or T-7-T-6 which reassemble to the trimer at pH = 7.0. A linear three-frame origami structure bridged by duplexes including caged i-motif units undergoes pH-stimulated isomerization to a bent structure (pH = 4.5) through the formation of i-motif complex and bridging T-A center dot T triplex units.