Nature often uses large biomolecules to capture and remove small targets from a mixture, in the same conceptual way that a fisherman employs a net to secure a fish. But biomolecules are relatively fragile which limits their utility, and there is a need for synthetic mimics that can capture specific targets, such as colored dyes, with high affinity and selectivity. The Macromolecular, Supramolecular and Nanochemistry Program supports Professor Bradley Smith of the University of Notre Dame to synthesize and study cylinder-shaped molecules that capture dyes on the surface of small beads. The dye coated beads can be easily detected using a cheap camera or even the naked eye. They are potentially useful in environmental and biomedical applications. The research activities provide rigorous student training in chemical synthesis and data analysis, as well as extensive experience in oral and written presentations. As part of a pedagogical project, Professor Smith and his students are upgrading the free internet workbook Organic Structure Elucidation by including a series of video answers to the problems. Free and unrestricted access to the video answers helps students who lack access to advanced educational resources or experienced instructors.
The project builds on a recent discovery that water soluble squaraine dyes with appended polyethylene glycol chains can be threaded with extremely high affinity by a water soluble tetralactam macrocycle containing anthracene side-walls. The term Synthavidin (synthetic avidin) is the generic name for this host/guest association system. The research develops the underlying synthetic and supramolecular chemistry to produce strong and rapid capture of highly fluorescent squaraine dyes in water, and complexation-induced changes in absorption and fluorescence properties. The work produces molecular design concepts that guide supramolecular researchers towards high affinity receptors for operation in water. The bead capture assay is endowed with two powerful attributes, namely, the capability to remove enzyme cleaved fluorescent dye from turbid media and the creation of amplified signal due to self-assembly of a hyperbranched fluorescent shell around the bead. The assay design is generalizable and can be expanded to include many types of cleavage enzymes.
