Pillararene Sulfates: Understanding and Using their Ultratight Binding

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With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Lyle Isaacs of the University of Maryland-College Park will study the preparation and molecular recognition properties of a class of molecular containers known as pillararene sulfates. In everyday life, containers are used to store beverages and food, to ship items to specific destinations, and to organize objects. Similarly, when a molecular container encapsulates a smaller molecule, advantageous improvements in chemical and biological properties can occur including better solubility, brighter colors, and lower toxicity. The Isaacs group has found that pillararene sulfates encapsulate smaller molecules exceptionally strongly in water and will perform studies to understand the origins of this strong binding and use them in prototypical applications such as chemical and biological sensing and environmental remediation. The work has significant broader impacts in that undergraduates and graduate students will be trained as interdisciplinary scientists crucial for the US workforce. Furthermore, the data sets generated by the Isaacs group will allow computational chemists to improve their computational methods via SAMPL(statistical assessment of the modeling of proteins and ligands) challenges. Dr. Isaacs will incorporate Virtual Reality headsets into his (under)graduate courses to enhance the students ability to visualize molecules in three dimensions. Finally, the pillararene sulfates to be prepared by the Isaacs group are likely to be adapted by other researchers for diverse applications including for the encapsulation of polymers, as well as for drug delivery, and biological imaging.The water soluble pillar[6]arene derivative WP6 bearing carboxylic acid groups has been well studied over the past decade. Professor Isaacs and his students found that pillar[6]arene sulfates bind up to 10,000-fold more tightly than the anionic, water-soluble pillararene, WP6, toward cationic guests in aqueous solution. Professor Isaacs' research group will systematically vary each structural component of pillararene sulfates by synthetic organic chemistry and subsequently investigate their molecular recognition capabilities toward panels of hydrophobic cations by a combination of NMR spectroscopy, X-ray crystallography, UV/vis and fluorescence spectroscopy, and isothermal titration calorimetry to uncover the origins of their exceptionally strong binding abilities. Pillararene sulfates that feature a single reactive functional group will be prepared; this will allow them to be appended to more complex systems such as polymers and solid phase supports. The abilities of the new pillararene sulfates will be explored in chemically and biologically relevant contexts as components of novel sensing, separation, and sequestration systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.