The Gagné Lab is interested in the development of new synthetic methods for complex bond constructions. To mimic sterol biosynthesis, we have developed several "carbophilic" late metal catalysts (Pd, Pt, and Au) for alkene and allene activation, while in other projects we seek new catalysts for glycosidic C-O bond activation. The goal in this latter project is to use polysaccharides as renewable feedstocks for complex molecule synthesis. A third major thrust is in dynamic combinatorial chemistry (DCC), a dynamic templating strategy that selects for new receptors under competitive binding conditions. This strategy is additionally being used for new catalyst discovery.
The research in the Rubinstein Group is in the field of polymer theory and computer simulations. The unique properties of polymeric systems are due to the size, topology and interactions of the molecules they are made of. Our goal is to understand the properties of various polymeric systems and to design new systems with even more interesting and useful properties. Our approach is based upon building and solving simple molecular models of different polymeric systems. The models we develop are simple enough to be solved either analytically or numerically, but contain the main features leading to unique properties of real polymers. Computer simulations of our models serve as an important bridge between analytical calculations and experiments.
Dark-field microscopy, DFM, is widely used to optically image and spectroscopically analyze nanoscale objects. In a typical DFM configuration, a sample is illuminated at oblique angles and an objective lens collects light scattered by the sample at a range of lower angles. As demonstrated in an article published as the cover of ACS Photonics, researchers in the Cahoon Group have developed waveguide scattering microscopy, WSM, as an alternative technique to image and analyze photonic nanostructures. WSM uses an incoherent white-light source coupled to a dielectric slab waveguide to generate an evanescent field that illuminates objects located within several hundred nanometers of the waveguide surface.
Using standard microscope slides or coverslips as the waveguide, the group demonstrate high-contrast dark-field imaging of nanophotonic and plasmonic structures such as Si nanowires, Au nanorods, and Ag nanoholes. Scattering spectra collected in the WSM configuration show excellent signal-to-noise with minimal background signal compared to conventional DFM. In addition, the polarization of the incident field is controlled by the direction of the propagating wave, providing a straightforward route to excite specific optical modes in anisotropic nanostructures by selecting the appropriate input wavevector. Considering the facile integration of WSM with standard microscopy equipment, the Cahoon Group scientists anticipate it will become a versatile tool for characterizing photonic nanostructures.
Assistant Professor Leslie Hicks has been awarded the Arthur C. Neish Young Investigator Award. These awards are given each year by the Phytochemical Society of North America to outstanding early career scientists. The young investigator chosen will present their research at the annual meeting as part of the Arthur C. Neish Young Investigator Mini-symposium. Leslie made her presentation earlier this month at the 53rd Annual Meeting in Raleigh. Congratulations, Leslie!
Typically, diesel fuel is made from crude oil, but scientists can make high-grade diesel from coal, natural gas, plants or even agricultural waste, using a process called Fischer-Tropsch, or FT. Just about any carbon source is an option. FT Diesel is the ideal liquid transportation fuel for automobiles, trucks and jets. It's much cleaner burning than conventional diesel, and much more energy efficient than gasoline. But, FT Diesel is expensive to make and generates lots of waste.
With support from the National Science Foundation, NSF, and its Center for Enabling New Technologies Through Catalysis, CENTC, chemists from around the United States, including professor Maurice Brookhart from Carolina, are working together to improve the cost and energy efficiency of alternative fuels. CENTC scientists have invented and patented, and are bringing toward commercialization, catalysts that will convert light hydrocarbons into FT Diesel, improving the process, whether it's diesel made from traditional sources, such as oil, or alternative sources, such as biomass.
NSF: Miles O'Brien, Science Nation Correspondent; Ann Kellan, Science Nation Producer
Researchers in the Johnson Group, published in Organic Letters, describe the stereoselective synthesis of trisubstituted 2-trifluoromethyl pyrrolidines by asymmetric Michael addition/hydrogenative cyclization.
The direct organocatalytic addition of 1,1,1-trifluoromethylketones to nitroolefins proceeds under mild reaction conditions and low catalyst loadings to provide Michael adducts in high yield with excellent diastereo- and enantioselectivity. Catalytic hydrogenation of the Michael adducts stereoselectively generates 2-trifluoromethylated pyrrolidines bearing three contiguous stereocenters. The group members also describe a stereospecific route to epimeric 2-trifluoromethyl pyrrolidines from a common intermediate.
In vivo glucose biosensors have the potential to greatly improve the way diabetics manage their disease. Unfortunately, such devices do not function as intended, that is, reliably, after implantation due to inflammation and encapsulation due to the "foreign body response.” The Schoenfisch Group has for the last decade researched the benefits of materials that release nitric oxide, NO, to mitigate the foreign body response. In an article published in Analytical Chemistry, they describe the analytical performance benefits of a NO-releasing glucose biosensor percutaneously implanted in a swine model.
Needle-type glucose biosensors were modified with NO-releasing polyurethane coatings designed to release similar total amounts of NO for either rapid or slower durations, and remain functional as outer glucose sensor membranes. Relative to controls, NO-releasing sensors were characterized with improved numerical accuracy on days one and three.
The clinical accuracy and sensitivity of rapid NO-releasing sensors were superior to control and slower NO-releasing sensors at both one and three days after implantation. In contrast, the slower/extended NO-releasing sensors were characterized by shorter sensor lag times in response to intravenous glucose tolerance tests versus burst NO-releasing and control sensors. Collectively, these results highlight the great potential for NO release to enhance the analytical utility of in vivo glucose biosensors. Initial results also suggest that this analytical performance benefit is dependent on the NO-release duration.
The process of immobilizing enzymes onto solid supports for bioreactions has some compelling advantages compared to their solution-based counterpart including the facile separation of enzyme from products, elimination of enzyme autodigestion, and increased enzyme stability and activity. Researchers in the Soper Group, published in Analytical Chemistry report the immobilization of λ-exonuclease onto poly(methylmethacrylate) (PMMA) micropillars populated within a microfluidic device for the on-chip digestion of double-stranded DNA.
The group's results suggest that the efficiency for the catalysis of dsDNA digestion using λ-exonuclease, including its processivity and reaction rate, were higher when the enzyme was attached to a solid support compared to the free solution digestion. The results from this work will have important ramifications in new single-molecule DNA sequencing strategies that employ free mononucleotide identification.
At the Department of Chemistry, we feel strongly that diversity is crucial to our pursuit of academic excellence, and we are deeply committed to creating a diverse and inclusive community. We support UNC's policy, which states that "the University of North Carolina at Chapel Hill is committed to equality of opportunity and pledges that it will not practice or permit discrimination in employment on the basis of race, color, gender, national origin, age, religion, creed, disability, veteran's status, sexual orientation, gender identity or gender expression."