Rational Design of Abasic Site-Containing DNA Triplexes To Bind Small Molecules with Low Nanomolar Dissociation Constants.

design of functional biomacromolecules is of great interest to a wide range of fundamental science and technological applications, including understanding life evolution and biomacromolecular structures, developing novel catalysts, inventing medicines, and exploring high-performance materials. However, it is an extremely challenging task and its success is very limited. It requires a deep understanding of the relationships among the primary sequences, the 3D structures, and the functions of biomacromolecules. Herein, we report a rational, design of a DNA aptamer that can bind melamine with high specificity and high affinity (dissociation constant = 4.4 nM). The aptamer is essentially a DNA triplex, but contains an abasic site, to which the melamine binds. The aptamer-ligand recognition involves hydrogen-bonding, π-π stacking, and electrostatic interactions. This strategy has been further tested by designing aptamers to bind to guanosine. It is conceivable that such a rational strategy, with further development, would provide a general framework for designing functional DNA molecules.