Polymer-catalyzed DNA assembly relies on weak non-covalent interactions

In general, molecular interactions with high binding affinities are preferred when constructing self-assembly systems. Herein, we demonstrate that weak non-covalent interactions, although not advantageous in constructing thermodynamically stable assemblies, can play a vital role in regulating assembly kinetics. Positively charged polymer poly(lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) can enrich DNA strands and lower the activation barrier for DNA strand displacements. The acceleration effect versus affinity between polymers and DNA follows a volcano-like plot, akin to the law governing catalysts in covalent synthesis. Optimal acceleration is achieved when the affinity is neither too strong nor too weak (around 105 to 107 M−1). In this case, polymer-catalyzed DNA strand displacement follows an assembly-while-bound mechanism. Due to relatively weak and dynamic binding, DNA strands reversibly associate with and dissociate from PLL-g-PEG, enabling conformational adjustments of DNA that facilitate strand displacement. The volcano relationship and assembly-while-bound mechanism relying on weak interactions may be widely applicable in designing catalyzed-assembly systems.