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.
A recent C&E Cover Story entitled Chromatography In the Extremes featured the Jorgenson Group and current work in the lab focusing on improving the efficiency of liquid chromatographic separations. With the driving force being fast and effective separations, the Jorgenson Group specializes in LC separations using extremely small packing particles and high column pressures. Current group members are looking into improving column packing technologies for micron size porous particles as well as alternative packing materials for enhanced separations.
Parastoo Hashemi, a Postdoctoral Scholar in the Wightman Group, has been selected as the student recipient of the 2010 University Awards for the Advancement of Women. This prestigious award, given by the Chancellor's Office, is in its fifth year and was created to recognize individuals for their contributions on behalf of women at the University of North Carolina at Chapel Hill.
Suspensions are of wide interest and form the basis for many smart fluids. For most suspensions, the viscosity decreases with increasing shear rate; that is, they shear thin. Few are reported to do the opposite, that is, shear thicken, despite the longstanding expectation that shear thickening is a generic type of suspension behavior. As published in Nature Materials, researchers in the DeSimone Group with collaborators at the University of Chicago and Liquidia Technologies have resolved this apparent contradiction.
The team has demonstrated that shear thickening can be masked by a yield stress and can be recovered when the yield stress is decreased below a threshold. They have shown the generality of this argument and have quantified the threshold in rheology experiments where they controlled yield stresses arising from a variety of sources, including attractions from particle surface interactions, induced dipoles from applied electric and magnetic fields, as well as confinement of hard particles at high packing fractions. These findings open up possibilities for the design of smart suspensions that combine shear thickening with electro- or magnetorheological response.
Published in JACS, the Murray Group reports how electrospray ionization triple-quadrupole mass spectrometry of ca. 1.6 nm diameter thiolate-protected gold nanoparticles has been achieved at higher resolution than in previous reports. The results reveal the presence of nanoparticles with formulas Au144L60 and Au146L59, present in the sample as a mixture.
The improved resolution is based on lowering m/z by exchanging multiple [−SC11H22N(CH2CH3)3+] ligands into the original [−S(CH2)5CH3] ligand shell. The nanoparticles are thus intrinsically cationized and appear as a series of 10+ to 15+ mass spectral peaks. The assigned state of charge was confirmed by a collision-induced dissociation measurement.
The National Science Foundation, NSF, is celebrating the achievements of five leading Science and Technology Centers, STC, that have been conducting world-class research and education programs since 2000 in varied disciplines with NSF funding. Each STC received a total of $38 million under its own cooperative agreement with NSF that concluded in 2010. Among the five centers recognized is the Science and Technology Center for Environmentally Responsible Solvents and Processes under the direction of UNC Chemistry faculty member Joseph DeSimone.
This STC is the world's leading center for enabling and discovering sustainable processes and products that use CO2-related technology. In addition, by fostering innovation and applying its discoveries to the development of sustainable energy alternatives, medical diagnostics and therapeutics via targeted delivery, its achievements have had broad societal benefits, including the catalytic role of its launch of eight start-up companies. Additionally, they have successfully engaged the public in science through various forums, including the NBTC Nanobiotechnology Center's traveling exhibit, It's a Nanoworld.
The discovery of nitric oxide's biological roles has encouraged its investigation as a potential therapeutic for a number of disease states. Due to its rapid reactivity, many groups have investigated ways to facilitate the storage and controlled release of nitric oxide. Based on the ability to coordinate two moles of nitric oxide per precursor, N-diazeniumdiolates represent the most commonly employed nitric oxide donor scaffold. Nitric oxide release from diazeniumdiolates is proton-induced making them appropriate scaffolds for use in physiological systems.
As published in Organic Letters, researchers in the Schoenfisch Group have identified that current synthetic methods for preparing N-diazeniumdiolates using polyamine compounds may lead to the formation of potentially carcinogenic N-nitrosamine byproducts. Their findings indicate that the incidence of nitrosamine formation increases by up to 4 orders of magnitude for scaffolds containing multiple amines due to increased stabilization of an intermediate species via hydrogen bonding and solvent interactions. As the therapeutic effects of diazeniumdiolate derived nitric oxide have been shown to be beneficial, these results indicate the need for alternative methods for diazeniumdiolate synthesis to minimize the formation of nitrosamines. In addition, more stringent characterization of these nitric oxide donors is required to confirm the absence of potentially carcinogenic byproducts.
Carolina Chemistry Assistant Professor David Nicewicz has been awarded an Eli Lilly New Faculty Award. This award is given annually to two recently hired assistant professors in organic chemistry based on their pre-academic research success. The unrestricted monetary gift is designed to aid the new faculty member in starting his/her independent research program.