The Johnson Group recently completed an asymmetric synthesis of the squalene synthesis inhibitor zaragozic acid C. The synthesis featured an interesting controlled oligomerization cascade to establish much of the stereochemically and functionally complex core. More broadly, the work asks if the lessons of polymer synthesis can be applied in the realm of natural product synthesis through the application of tailor-made reagents with the appropriate trigger. This work was highlighted in Science and Chemical and Engineering News.
The Gagné Lab is interested in the development of new synthetic methods for complex bond constructions. To mimic sterol biosynthesis, we have developed several "carbophilic" late metal catalysts (Pd, Pt, and Au) for alkene and allene activation, while in other projects we seek new catalysts for glycosidic C-O bond activation. The goal in this latter project is to use polysaccharides as renewable feedstocks for complex molecule synthesis. A third major thrust is in dynamic combinatorial chemistry (DCC), a dynamic templating strategy that selects for new receptors under competitive binding conditions. This strategy is additionally being used for new catalyst discovery.
Electrochemical detection with carbon-fiber microelectrodes has become an established method to monitor directly the release of dopamine from neurons and its uptake by the dopamine transporter. With constant potential amperometry (CPA), the measured current provides a real time view of the rapid concentration changes, but the method lacks chemical identification of the monitored species and markedly increases the difficulty of signal calibration. Monitoring with fast-scan cyclic voltammetry (FSCV) allows species identification and concentration measurements but often exhibits a delayed response time due to the time-dependent adsorption/desorption of electroactive species at the electrode.
Researchers in the Wightman Group, as published in ACS Chemical Neuroscience sought to improve the temporal resolution of FSCV to make it more comparable to CPA by increasing the waveform repetition rate from 10 to 60 Hz with uncoated carbon-fiber electrodes. The faster acquisition led to diminished time delays of the recordings that tracked more closely with CPA measurements. The measurements reveal that FSCV at 10 Hz underestimates the normal rate of dopamine uptake by about 18%. However, FSCV collection at 10 and 60 Hz provide identical results when a dopamine transporter (DAT) blocker such as cocaine is bath applied.
To further verify the utility of this method, the group used transgenic mice that overexpress DAT. After accounting for the slight adsorption delay time, FSCV at 60 Hz adequately monitored the increased uptake rate that arose from overexpression of DAT and, again, was similar to CPA results. Furthermore, the utility of collecting data at 60 Hz was verified in an anesthetized rat by using a higher scan rate (2400 V/s) to increase sensitivity and the overall signal.
As described in Advanced Materials, the Lin Group has developed a new metal-organic framework (MOF)-templated method for the synthesis of a mixed metal oxide nanocomposite with interesting photophysical properties. Fe-containing nanoscale MOFs are coated with amorphous titania, which are then are calcined to produce crystalline composite octahedral nanoshells with hematite Fe2O3 nanoparticles embedded in anatase TiO2.
This material enables photocatalytic hydrogen production from water using visible light, which cannot be achieved by either Fe2O3 or TiO2 alone or a mixture of the two. This versatile MOF-templated nanocomposite synthesis procedure could be readily modified, by varying the type of MOF and the coating material, to prepare new materials with desirable synergistic properties.
Alexandru Bacanu, a junior working with John P. Barker Distinguished Professor
Dr. Michael Rubenstein, has won a 2012 Goldwater Scholarship.
Congress established the Barry M. Goldwater Scholarship and Excellence in Education Program in 1986 to honor the late Barry M. Goldwater of Arizona, who served in the U.S. Senate for 30 years. They award scholarships to outstanding college sophomores and juniors who intend to pursue careers in mathematics, the natural sciences or engineering.
Congratulations, Alexandru!
You can read about the work Alexandru has been doing with Dr. Rubinstein in the Spring 2012 issue of Carlolina Scientific.
Congratulations to all students who were recognized at this year's Chemistry Commencement ceremony. Chemistry is considered one of the most demanding degrees offered at Carolina.
Professor and Department Chair Matthew Redindo delivered the welcome address, after which followed the doctoral hooding ceremony, presided over by Professor Mark Schoenfisch, Director of Graduate Studies. Miss Eva Archer then delivered the undergraduate student commencement address.
Dr. Marcey Waters, Professor and Director of Undergraduate Studies presented the undergraduate student awards. Congratulations to all winners.
Francis P. Venable Medal
Matthew Detter
Sophie Liu
Emmett Gladstone Rand Premedical Scholarship
Ryan Gardner
Kathryn Magee
Garrick Talmadge
David L. Stern Scholarships in Chemistry
Xiaoling Zang
Merck Index Award
Stephen Barilovits IV
Srikar Bongu
Carrie Ann Largent Award
Sean Doris
Teresa Long
Hypercube Scholar Award
Hannah Gavin
Metal-organic frameworks, MOFs, represent a new class of structurally ordered hybrid materials whose properties can be fine-tuned at the molecular level to suit many applications. In particular, recent works from the Lin and Meyer groups have demonstrated rapid energy migration over long distances and efficient electron transfer quenching at the interfaces of emitting MOFs.
MOFs with triplet metal-to-ligand charge transfer excited-states offer a promising scaffold for amplified quenching, a signal gain as a result of interactions between a sensing material and analytes accompanied by rapid energy migration. A remarkable example of MOF-based amplified quenching has been published in JACS using Ru(II)-bpy based MOFs and cationic quenchers. The MOF surface is partially terminated with carboxylate groups that have strong non-covalent interactions with cationic quenchers and lead to quenching enhancements of up to 7000-fold compared to a model complex. This work points to the potential of designing MOF-based sensors for sensitive and selective sensing of many analytes via amplified quenching.