(659h) Liquid Crystal Orientational Transformations Induced By Interfacial Biomolecular Interactions

We have studied how biomolecular interactions at interfaces, in particular aptamer-ligand binding events, can induce orientational transformations in an adjacent bulk liquid crystal phase.  Physical properties of liquid crystalline materials such as long-range orientational order, responsiveness to external stimuli, and optical anisotropy make them advantageous for use as transduction elements in sensing applications. Thus, we have demonstrated that aptamer-ligand binding events, involving small molecules, at a surfactant-laden aqueous/liquid crystal (LC) interface can trigger sensitive and selective LC orientational transformations.  Mechanistic studies involving circular dichroism and resonance energy transfer measurements revealed that the LC reorientation was directly related to a conformational change of the aptamer upon ligand binding. Specifically, under conditions where aptamer-ligand binding induced a conformational change from a relaxed random coil to more intricate secondary structures that enclose hydrophobic nucelobases (eg. double helix, G-quadruplex); an LC orientational transformation from planar to homeotropic was observed.  These observations improve our understanding of how relatively subtle changes in the hydrophobicity of biomolecules at interfaces can induce changes to the associated interfacial structure. Furthermore, we demonstrate the potential for a label-free LC-based detection system that can simultaneously detect the presence of both small molecules and nucleic acids.