Analytical Chemistry, in its 12th issue and 80th volume in 2008, featured a fundamental review of electrochemical sensors written by past and present Schoenfisch Lab members B.J. Privett, Jae Ho Shin, and Mark H. Schoenfisch. The review detailed the 200 most significant advancements in the fields of potentiometric, voltammetric, and electrochemical biosensors from publications throughout the preceding two years. Sections of the invited review highlighted advancements in topics of notable interest to the Schoenfisch group, such as the voltammetric detection of nitric oxide as well as the employment of nitric oxide-releasing sensor coatings used to enhance the utility and lifetime of implanted in vivo sensors.
Venable Hall was a treat for the senses. In the cold months, students would compete for the good seats near the radiators in the second floor classrooms. In the warm months, the window air conditioning units were insufficient, so we would pry open the windows. I am not sure how the grounds crews were always able to plan their mowing activities for the times I would be lecturing, but somehow I managed to speak loudly over the sounds of mowing. As for the floor plan of Venable, the second floor was pure simplicity, but the maze that was the first floor was another matter, made worse by a room numbering system that defied deciphering. But the smells of Venable are what are most memorable; generally a bit humid and musty, but varying with the time of year. And in the spring, the smell of newly mown grass that wafted through the open windows of the classroom.
James Jorgenson - Department Chair, 2000 - 2005
As reported in the October 23, 2009, issue of the journal Science, Carolina chemists in collaboration with colleagues at the University of Washington have taken an important step in converting methane gas to a liquid, potentially making it more useful as a fuel and as a source for making other chemicals.
The carbon-hydrogen bonds of alkanes are weak ligands and thus reports of isolation or spectroscopic observation of alkane complexes in solution are extremely rare. Nevertheless, such complexes are postulated as intermediates that form prior to C-H bond scission in most oxidative addition reactions of alkanes. The Shilov system for catalytic conversion of methane to methanol is thought to involve a Pt(II) methane complex as a key intermediate. While a postdoctoral fellow in the Brookhart Group, Wes Bernskoetter, now on the faculty at Brown, succeeded in preparing the first solution-stable, NMR-observable transition metal complex of the simplest alkane, methane (CH4).
The methane complex was obtained by low temperature protonation of a pincer rhodium methyl complex and fully characterized by 1H, 13C and 31P NMR spectroscopy. Cindy Schauer, co-author of the study, carried out DFT calculations that suggest one C-H bond interacts preferentially with the Rh center to form a three-center, two-electron bond, as per the above figure. The Brookhart Group hopes that investigation of the properties of this and other methane complexes may lead to more efficient catalysts for functionalization of alkanes.
Protein tyrosine phosphatases (PTPs) regulate a broad range of cellular processes including proliferation, differentiation, migration, apoptosis, and immune responses. Dysfunction of PTP activity is associated with cancers, metabolic syndromes, and autoimmune disorders. Consequently, small molecule PTP inhibitors should serve not only as powerful tools to delineate the physiological roles of these enzymes in vivo but also as lead compounds for therapeutic development.
In a collaborative work published in JACS, the Lawrence Group describes a novel stepwise fluorophore-tagged combinatorial library synthesis and competitive fluorescence polarization screening approach that transforms a weak and general PTP inhibitor into an extremely potent and selective TC-PTP inhibitor with highly efficacious cellular activity. The result serves as a proof-of-concept in PTP inhibitor development, as it demonstrates the feasibility of acquiring potent, yet highly selective, cell permeable PTP inhibitory agents. Given the general nature of the approach, this strategy should be applicable to other PTP targets.
This past summer 13 UNC students took their Chem 262 during the second summer session, not in Chapel Hill, but in Sevilla, Spain. They were the inaugural group of students who took advantage of a new study abroad initiative in which students can elect to take this important course, taught in English, by a UNC system professor in Spain.
In addition, the students took a 3 credit Spanish class, SPAN 104 or higher, taught by a Spanish professor from Sevilla. Students lived for the 5-6 weeks with Spanish families, where they ate all their meals. The organic courses was taught this year by Prof. Phil Brown of NCSU. Some of these students were so thrilled that they are opting to go back to Spain next year as exchange students, where they get to take their chemistry courses in Spanish.
Serotonin, also known as 5-HT is an important molecule in the brain that is implicated in mood and emotional processes. Although there is a heavy pharmaceutical emphasis on serotonin's involvement in many neurological disorders, in vivo, its dynamic release and uptake kinetics are poorly understood. This is due to a lack of analytical techniques for its rapid measurement. Whereas fast-scan cyclic voltammetry with carbon fiber microelectrodes is used frequently to monitor subsecond dopamine release in freely moving and anesthetized rats, the electrooxidation of serotonin forms products that quickly polymerize and irreversibly coat the carbon electrode surface.
In a paper published in Analytical Chemistry, the Wightman Group identifies the root of this fouling to not only be due to serotonin, but also to the negatively charged extracellular metabolites of serotonin, present in 200−1000 times the concentration of serotonin in vivo. To impede access of these negatively charged species, a thin layer of Nafion, a cation exchange polymer, was electrodeposited onto cylindrical carbon-fiber microelectrodes. The team visually confirmed the presence of the Nafion film using scanning electron microscopy and showed that the signals for negatively charged species were diminished. Interestingly, the properties of the Nafion also increased sensitivity to serotonin, providing an electrochemical signature of serotonin that could be verified in vitro. In vivo, the team used physiological, anatomical, and pharmacological evidence to validate the signal as serotonin. Using Nafion-modified microelectrodes, the Wightman Group presents the first endogenous recording of serotonin in the mammalian brain.
Indium tin oxide (ITO) is a transparent conductor used for applications ranging from solar cells to neurobiology. Tailoring ITO surfaces with a range of functional groups is challenging due to the difficulty in synthesizing phosphonate or siloxane terminated molecules. As reported in Advanced Materials, the Yousaf Group has developed a chemoselective immobilization strategy to tailor ITO surfaces by selectively oxidizing hydroxyl-terminated phosphonate SAMs to aldehydes, using microfluidics, followed by reaction with oxyamine-containing ligands. This rapid, inexpensive, and selective, on-chip activation allows for a wide range of ligands to be tethered onto ITO. Electrochemistry, contact angle, and XPS characterize the alcohol oxidation and subsequent reactivity. They also show control of ligand density and patterned cells on the newly generated aldehyde-terminated ITO surface.
This methodology allows for the generation of patterned complex surface chemistry on ITO surfaces from a simple hydroxyl-terminated SAM surface. The ability to generate complex surfaces with simple starting materials and minimal to no synthesis may have wide-ranging utility for numerous applications in molecular electronics and biotechnology including co-culture and cell arrays.
Cellular RNA molecules undergo complex folding transitions to form specific, biologically active, three-dimensional structures. A persistent and poorly explained observation is that many RNAs fold very slowly, on timescales requiring minutes or longer. Slow folding ultimately governs the rate at which an RNA can perform its biological function.
In work reported in PNAS, Stefanie Mortimer in the Weeks Lab used time-resolved SHAPE chemistry to show that slow folding at a single nucleotide in the unusual C2'-endo conformation constitutes the rate-determining step for folding a large 50 kDa RNA. Nucleotides in the C2'-endo conformation are relatively rare but are highly overrepresented in functionally critical RNA motifs. This work thus identifies a surprisingly simple, but likely ubiquitous, mechanism for controlling biological processes involving RNA.