Gas Phase Supramolecular Characterization

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With support from the Chemical Measurement and Imaging program, Prof. David Dearden and his group at Brigham Young University are devising new approaches to the detection and characterization of prototypical molecular devices based on pumpkin-shaped molecules (named cucurbiturils, after the Latin name for "pumpkin") that constitute some of the smallest possible containers. The methods being developed complement existing techniques by providing better sensitivity. They include the first infrared multiphoton dissociation studies of these materials, essentially using infrared laser light to take "snapshots" that reveal the way the devices fit together. Cucurbiturils and related "containers" are being investigated in other laboratories for potential applications in such diverse areas as components of molecular machines; in drug encapsulation, protection, and delivery; and in sensitive new analytical assays such as the direct detection of insulin levels in the blood (relevant to the detection and treatment of diabetes). It is widely recognized that the binding properties of cucurbiturils are sensitively dependent on solvents and counterions, yet the reasons for this dependence are not clearly understood. Hence, these fundamental gas-phase studies of structures in the absence of solvent and counterions are vital to gain understanding needed to facilitate future applications, addressing questions such as how trapping molecules inside the cavity affects the binding of cations on the rims, the mechanism of exchange of bound/trapped species, and the origin of the large shifts in acidity that occur for trapped guests.The characterization methods being developed will enable applications of this "supramolecular" chemistry that may ultimately impact manufacturing, computing, and medicine. The techniques will also be immediately useful to biomolecular studies involving nature's "molecular machines," proteins. The work will also have important educational benefits. Graduate students will be trained in advanced techniques for high performance mass spectrometry that are vital for the biotechnology industry and the emerging field of proteomics. A parallel aim is to attract talented undergraduate students to chemical research. Toward this aim, the instrumentation supported is also used in undergraduate courses in analytical and physical chemistry, providing direct experience with advanced techniques most students would not otherwise see outside of graduate school.