The Forbes Group seeks to understand the structure, reactivity and dynamics of free radicals in a variety of media. We are especially interested in how radicals behave in confined environments such as micelles, nanocrystals polymers, and host-guest complexes. Using time–resolved and steady-state magnetic resonance spectroscopies (EPR and NMR), our current projects include investigation of the role of spin in proton-coupled electron transfer reactions, the spectroscopic signatures of free radicals trapped in organic nanocrystals, the degradation of novel polymers in solution, the location of singlet oxygen in photodynamic therapy for cancer treatment, and the adhesion of polymers to each other via grafting reactions. Previous projects have included the elucidation of the mechanism of formation of "skunky" beer by sunlight, and the formation of free radicals upon UV exposure to commercial sunless tanning lotions.
The Redinbo Laboratory uses the tools of structural, molecular and chemical biology to examine a range of dynamic cellular processes central to human health. Current projects include the discovery of new antimicrobials targeted to drug-resistant bacteria, the design of novel proteins engineered to detect and eliminate toxic chemicals, and the development of small-molecule to cell-based methods to improve anticancer chemotherapeutics. In addition, we continue to focus on determining the crystal structures of macromolecular complexes, including those involving human nuclear receptors central to transcriptional regulation, bacterial proteins involved in DNA manipulation and human cell contact, and enzymes central to key cellular processes.
Artificial photosynthesis and the production of solar fuels could be a key element in a future renewable energy economy providing a solution to the energy storage problem in solar energy conversion. Published in PNAS and chosen as "paper of the month" by The Latest Science, researchers in the Meyer Group describe a hybrid strategy for solar water splitting based on a dye sensitized photoelectrosynthesis cell.
Solar water splitting into H2 and O2 with visible light has been achieved by a molecular assembly. The dye sensitized photoelectrosynthesis cell configuration combined with core–shell structures with a thin layer of TiO2 on transparent, nanostructured transparent conducting oxides (TCO), with the outer TiO2 shell formed by atomic layer deposition. In this configuration, excitation and injection occur rapidly and efficiently with the injected electrons collected by the nanostructured TCO on the nanosecond timescale where they are collected by the planar conductive electrode and transmitted to the cathode for H2 production. This allows multiple oxidative equivalents to accumulate at a remote catalyst where water oxidation catalysis occurs.
Scientists in the Johnson Group, in collaboration with researchers from GlaxoSmithKline, as published in Organic Letters, show how a high throughput screening enabled the development of a copper-based catalyst system for the asymmetric hydrogenation of prochiral aryl and heteroaryl ketones that operates at H2 pressures as low as 5 bar.
A ligand combination of (R,S)-N-Me-3,5-xylyl-BoPhoz and tris(3,5-xylyl)phosphine provided benzylic alcohols in good yields and enantioselectivities. The electronic and steric characteristics of the ancillary triarylphosphine were important in determining both reactivity and selectivity.
There are many potential benefits of converting biomass to fuels and feedstocks. In particular, the widespread availability and built-in stereochemistry of carbohydrates make them attractive starting materials for the production of value-added products. However, the large number of oxygen atoms relative to the number of carbon atoms renders carbohydrates "overfunctionalized" for many applications.
Researchers in the Gagné Lab recently published a method in Angewandte Chemie for using a commercially available non-metallic catalyst to remove some or all of the oxygen functionalities and replace them with hydrides. Even robust compounds such as methylcellulose are deoxygenated under the optimized conditions. The hydride equivalent is provided by an alkylsilane, and the identity of the silane can be used to control whether complete deoxygenation occurs to give fuel-like hydrocarbons or whether partial deoxygenation occurs, giving feedstock products with well-defined stereochemistry that are difficult to access with currently known methods.
Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory, researchers in the Rubinstein Group, as published in Macromolecules, studied a simple model of autonomic self-healing of unentangled polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the sticky end of another chain. The group studied the reaction kinetics of reversible bonds in this simple model and analyzed the different stages in the self-repair process.
The team observed the slowest formation of bridges for self-adhesion after bringing into contact two bare surfaces with equilibrium, very low, density of open stickers in comparison with self-healing. The primary role of anomalous diffusion in material self-repair for short waiting times is established, while at long waiting times the recovery of bonds across fractured interface is due to hopping diffusion of stickers between different bonded partners. Acceleration in bridge formation for self-healing compared to self-adhesion is due to excess nonequilibrium concentration of open stickers. Full recovery of reversible bonds across fractured interface, formation of bridges, occurs after appreciably longer time than the equilibration time of the concentration of reversible bonds in the bulk.
In studying a material that prevents marine life from sticking to the bottom of ships, researchers led by Carolina Chemistry's Joseph DeSimone, have identified a surprising replacement for the only inherently flammable component of today's lithium-ion batteries: the electrolyte.
The work, published in the Proceedings of the National Academy of Sciences, not only paves the way for developing a new generation lithium-ion battery that does not spontaneously combust at high temperatures, but also has the potential to —after recent lithium battery fires in Boeing 787 Dreamliners and Tesla Model S vehicles— renew consumer confidence in a technology that has attracted significant concern.
Published in Analytical Chemistry, scientists in the Allbritton Group in collaboration with colleagues from Pharmacology, Biostatistics and Endodontics, and Biomedical Engineering, all at UNC, and the National Health and Environmental Effects Research Laboratory, describe a novel method for the measurement of protein tyrosine phosphatase, PTP, activity in single human airway epithelial cells, hAECs, using capillary electrophoresis.
Their technique involved the microinjection of a fluorescent phosphopeptide that is hydrolyzed specifically by PTPs. Initial results were then extended to a more physiologically relevant model system: primary hAECs cultured from bronchial brushings of living human subjects. The results demonstrate the utility and applicability of this technique for the ex vivo quantification of PTP activity in small, heterogeneous, human cells and tissues.
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."