The cocaine-binding aptamer is unusual in that it tightly binds molecules other than the ligand it was selected for. Here, we study the interaction of the cocaine-binding aptamer with one of these off-target ligands, quinine. Isothermal titration calorimetry was used to quantify the quinine-binding affinity and thermodynamics of a set of sequence variants of the cocaine-binding aptamer. We find that the affinity of the cocaine-binding aptamer for quinine is 30-40 times stronger than it is for cocaine. Competitive-binding studies demonstrate that both quinine and cocaine bind at the same site on the aptamer. The ligand-induced structural-switching binding mechanism of an aptamer variant that contains three base pairs in stem 1 is retained with quinine as a ligand. The short stem 1 aptamer is unfolded or loosely folded in the free form and becomes folded when bound to quinine. This folding is confirmed by NMR spectroscopy and by the short stem 1 construct having a more negative change in heat capacity of quinine binding than is seen when stem 1 has six base pairs. Small-angle X-ray scattering (SAXS) studies of the free aptamer and both the quinine- and the cocaine-bound forms show that, for the long stem 1 aptamers, the three forms display similar hydrodynamic properties, and the ab initio shape reconstruction structures are very similar. For the short stem 1 aptamer there is a greater variation among the SAXS-derived ab initio shape reconstruction structures, consistent with the changes expected with its structural-switching binding mechanism.

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The steel frame reinforced with steel shear wall is a lateral load resisting system and has higher strength and shear performance than the concrete shear wall system. Especially, using corrugated steel plates in these shear wall systems improves out-of-plane stiffness and flexibility in the deformation along the corrugation. In this paper, a cyclic loading test of this steel frame reinforced with trapezoidal-corrugated steel plate was performed to evaluate the structural performance. The hysteresis behavior and the energy dissipation capacity of the steel frame were also compared according to the corrugated direction of the plate. For the test, one simple frame model without the wall and two frame models reinforced with the plate are considered and designed. The test results showed that the model reinforced with the corrugated steel plate had a greater accumulated energy dissipation capacity than the experimental result of the non-reinforced model. Furthermore, the energy dissipation curves of two reinforced frame models, which have different corrugated directions, produced similar results.

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