The Jeff Johnson Group focuses on the development of new synthetic methods for the assembly of stereochemically complex small molecules. We are particularly interested in the design and synthesis of tailor-made reagents and catalysts for multicomponent reactions. In our recent investigations of several interesting problems, our continuing interest in the exploitation of ring strain as a source of novel reactivity led us to some mechanistically unusual heterocycle-forming cycloadditions of cyclopropanes and aldehydes. On another front, we are interested in the development of dipolar synthons for the coupling of complementary nucleophilic and electrophilic reaction partners. Our development of silyl glyoxylate reagents is an example of work in this area.
An undergraduate research project is an exciting and rewarding experience. Undergraduate research can help you acquire a spirit of inquiry, initiative, independence, sound judgment, patience, persistence, alertness, and the ability to use the chemical literature. The Department strongly endorses undergraduate research as one of the potentially most rewarding aspects of your undergraduate experience.
Although successful completion of an undergraduate research project is a requirement for graduation with Honors or Highest Honors, it is not necessary to be a participant in the honors program to undertake a research project. Visit the Office for Undegraduate Research to learn where "your curiosity can lead you."
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.
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
Neurovascular coupling is understood to be the underlying mechanism of functional hyperemia, but the actions of the neurotransmitters involved are not well characterized. In an article published in the Journal of Cerebral Blood Flow & Metabolism, researchers in the Wightman Group investigate the local role of the neurotransmitter norepinephrine in the ventral bed nucleus of the stria terminalis, vBNST, of an anesthetized rat by measuring O2, which is delivered during functional hyperemia. Extracellular changes in norepinephrine and O2 were simultaneously monitored using fast-scan cyclic voltammetry. Introduction of norepinephrine by electrical stimulation of the ventral noradrenergic bundle or by iontophoretic ejection induced an initial increase in O2 levels followed by a brief dip below baseline.
Supporting the role of a hyperemic response, the O2 increases were absent in a brain slice containing the vBNST. Administration of selective pharmacological agents demonstrated that both phases of this response involve β-adrenoceptor activation, where the delayed decrease in O2 is sensitive to both α- and β-receptor subtypes. Selective lesioning of the locus coeruleus with the neurotoxin DSP-4 confirmed that these responses are caused by the noradrenergic cells originating in the nucleus of the solitary tract and A1 cell groups. Overall, these results support that non-coerulean norepinephrine release can mediate activity-induced O2 influx in a deep brain region.
William Black, a graduate student in the Ramsey Group, received the Csaba Horváth Young Scientist Award presented at the 41st International Symposium on High Performance Liquid Phase Separations and Related Techniques, HPLC 2014. The purpose of the award is to honor the memory of Csaba Horváth and recognize his contributions to HPLC, including his interest in fostering the careers of young people in separations science and engineering.
Oral presenters less than 35 years of age are eligible for the award and thus candidates include graduate students, postdocs, and assistant professors. Will was selected from over 50 applicants as one of eight finalists and presented his research on "Integrating Solid Phase Extraction with Microchip Capillary Electrophoresis-Electrospray Ionization." The award includes an invitation to speak at the HPLC 2015 symposium in Geneva Switzerland, a grant to support travel to that meeting, and a trophy engraved with his name. This award has been presented annually at the HPLC meeting starting in 2006. Will kept the award on UNC-CH turf as last years award winner was James Grinias, presently a graduate student working in the Jorgenson Group.
The direct anti-Markovnikov addition of strong Bronsted acids to alkenes remains an unsolved problem in synthetic chemistry. Published in Nature Chemistry, researchers in the Nicewicz Group report an efficient organic photoredox catalyst system for the addition of HCl, HF and also phosphoric and sulfonic acids to alkenes, with complete regioselectivity. These transformations were developed using a photoredox catalyst in conjunction with a redox-active hydrogen atom donor.
The nucleophile counterion plays a critical role by ensuring high reactivity, with 2,6-lutidinium salts typically furnishing the best results. The nature of the redox-active hydrogen atom donor is also consequential, with 4-methoxythiophenol providing the best reactivity when 2,6-lutidinium salts are used. A novel acridinium sensitizer provides enhanced reactivity within several of the more challenging reaction manifolds. Thew work published by the Nicewicz team demonstrates how nucleophilic addition reactions mediated by photoredox catalysis can change the way electrophilic and homofugal precursors are constructed.
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."