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Research in the Nicewicz Group focuses on developing new catalysts and methods for organic synthesis. In particular, our group seeks to harness the power of photoinduced electron transfer processes to drive the development of new asymmetric bond forming reactions. Additionally, we seek to apply these new reactions to the synthesis of biologically-active, complex natural products.
New research from the You Group, in collaboration with researchers at NCSU, reveals that energy is transferred more efficiently inside of complex, three-dimensional organic solar cells when the donor molecules align face-on, rather than edge-on, relative to the acceptor. This finding may aid in the design and manufacture of more efficient and economically viable organic solar cell technology.
The paper appears online in Nature Photonics. Fellow NC State collaborators were John Tumbleston, Brian Collins, Eliot Gann, and Wei Ma. Liqiang Yang and Andrew Stuart from UNC-Chapel Hill also contributed to the work. The work was funded by the U.S. Department of Energy, Office of Science, Basic Energy Science, the Office of Naval Research, and the National Science Foundation.
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.
The biomimetic cyclization of polyene containing substrates to their polycyclic counterparts has long benefitted from the installation of highly nucleophilic terminating groups. The more challenging bio-like alkene terminating substrates have received considerably less attention.
Research in the Gagné Group published in the Journal of the American Chemical Society has detailed the Pt catalyzed cycloisomerization of strictly polyene containing substrates to polycles. Cyclization of acyclic polyene substrates to bi, tri and tetracyclic products is observed, forming up to five stereocenters in a single step.
An article titled "Catalytic Hydrotrifluoromethylation of Styrenes and Unactivated Aliphatic Alkenes via an Organic Photoredox System," published in the journal Chemical Science by Professor David Nicewicz, his postdoctoral assistant Dale Wilger, and graduate student Nathan Gesmundo, has been listed as one of the 25 most read articles of 2013.
Chemical Science is the Royal Society of Chemistry's flagship journal, publishing research articles of exceptional significance and high-impact reviews from across the chemical sciences. Research in Chemical Science is not only of the highest quality but also has excellent visibility.
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.
As presented in Chemical Communications, researchers in the Allbritton Group in collaboration with Qisheng Zhang, associate professor in UNC's School of Pharmacy, and his group, have published a fluorous tagging strategy coupled with enzymatic synthesis to efficiently synthesize multiple phosphatidylinositides (PIs). PIs and their derivatives are notorious for their structural complexity, with seven stereogenic centers and the hydroxyl groups around the inositol head unit having similar reactivity.
Most synthetic strategies require selective protection and deprotection of the hydroxyl groups, and usually take more than 15 steps to synthesize one PI. The work presented by the two groups introduces "fluorous enzymatic synthesis," where tandem enzymatic reactions are used to generate multiple probes after purification through fluorous solid phase extraction. These probes can then be used as enzyme reporters, or be directly immobilized on a fluorous surface to form a microarray to investigate protein-small molecule interactions. This strategy should also be applicable to other complex endogenous small molecules whose biosynthetic enzymes are well characterized.
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."