The Miller Group designs multifunctional catalysts for the sustainable synthesis of fuels and chemicals. One class of catalyst features a strongly donating pincer core in which one donor is also part of a crown ether macrocycle. The macrocycle acts as a cation receptor site, capable of switching on catalyst activity and tuning catalyst selectivity in a variety of organic transformations.
Another class of catalyst are designed to absorb visible light in order to enhance reactivity. Visible light-promoted hydride transfer reactions relevant to solar energy storage in chemical fuels, including photoelectrochemical hydrogen evolution, have been realized using this strategy.
Mechanistic understanding drives research in the group forward, facilitating progress on challenging reactions and helping define new ligand-assisted mechanistic pathways for such transformations.
Our focus in the Ashby Group is the synthesis of functional shape memory materials for biomedical applications. We have recently reported the topological control of mesenchymal stem cells by responsive poly(Îµ-caprolactone) surfaces in which we engineered a biocompatible shape memory surface to mechanically alter stem cell topology.
Group members are also developing scaffolds for nitric oxide release in collaboration with the Schoenfisch Group, and are working towards the synthesis of new iodinated polyesters for use in X-ray computed tomography.
Dr. F. Ivy Carroll, member of Carolina Chemistry's External Advisory Board, has been recognized by the American Chemical Society as a 2014 ACS Fellow. He is honored for his contributions to science, including the design and development of a diagnostic agent for Parkinson's disease and compounds as potential treatments for cocaine and nicotine addictions and other central nervous system disorders. He is also recognized for his long service to ACS.
Dr. Carroll is a Distinguished Fellow in medicinal chemistry with RTI International, which he joined in 1960. He has published more than 440 peer-reviewed publications, 34 book chapters, 43 patents, and more than 20 current patent applications. Among his many awards and recognitions are the 2010 North Carolina Award for Science, and the 2010 National Institute on Drug Abuse Public Service Award for Significant Achievement.
Published in Bioconjugate Chemistry, researchers in the Schoenfisch Group describe the synthesis of nitric oxide, NO, releasing quaternary ammonium, QA, functionalized generation 1, G1, and generation 4, G4, poly(amidoamine), PAMAM, dendrimers. Dendrimers were modified with QA moieties of different alkyl chain lengths, such as methyl, butyl, octyl, dodecyl, via a ring-opening reaction. The resultant secondary amines were then modified with N-diazeniumdiolate NO donors to yield NO-releasing QA-modified PAMAM dendrimers capable of spontaneous NO release.
The bactericidal efficacy of individual, non-NO-releasing, and dual action, NO-releasing, QA-modified PAMAM dendrimers was evaluated against Gram-positive Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa bacteria. Bactericidal activity was found to be dependent on dendrimer generation, QA alkyl chain length, and bacterial Gram class for both systems. Shorter alkyl chains, such as methylQA and butylQA, demonstrated increased bactericidal activity against P. aeruginosa versus S. aureus for both generations, with NO release markedly enhancing overall killing.
According to Professor DeSimone and his Project Manager, Crista Farrell, a new report from the National Research Council provides an ideal opportunity for considering what is known about the power of diversity in groups and how this knowledge may be used in discussions of convergence as a conceptual framework for problem-solving and innovation in the 21st century.
Their Editorial, Driving Convergence with Human Diversity, published in Science Translational Medicine, discusses the role and power of diversity in day-to-day research practices, and emphasizes following the NRC report's recommendation of "adopting inclusive attitudes toward diversity and using management strategies to foster diversity."
The intracellular milieu differs from the dilute conditions in which most biophysical and biochemical studies are performed. This difference has led both experimentalists and theoreticians to tackle the challenging task of understanding how the intracellular environment affects the properties of biopolymers. Despite a growing number of in-cell studies, there is a lack of quantitative, residue-level information about equilibrium thermodynamic protein stability under nonperturbing conditions.
William Monteith and Professor Gary Pielak, published in PNAS, report the use of NMR-detected hydrogen–deuterium exchange of quenched cell lysates to measure individual opening free energies of the 56-aa B1 domain of protein G (GB1) in living Escherichia coli cells without adding destabilizing cosolutes or heat. Comparisons to dilute solution data, pH 7.6 and 37 °C, show that opening free energies increase by as much as 1.14 ± 0.05 kcal/mol in cells. Importantly, this research also shows that homogeneous protein crowders destabilize GB1, highlighting the challenge of recreating the cellular interior. William and Gary discuss their findings in terms of hard-core excluded volume effects, charge–charge GB1-crowder interactions, and other factors. The quenched lysate method identifies the residues most important for folding GB1 in cells, and should prove useful for quantifying the stability of other globular proteins in cells to gain a more complete understanding of the effects of the intracellular environment on protein chemistry.
Researchers in the Ashby and Sheiko groups have fabricated textured surfaces capable of reversibly changing in response to a thermal stimulus. These surfaces are fabricated with PRINT© molds provided by the DeSimone Lab, and could find use in applications requiring modular surface wetting or roughness. Reversibly switching topography on micrometer length scales greatly expands the functionality of stimuli-responsive substrates.
In an article published in ACS Applied Materials & Interfaces the groups report the first usage of reversible shape memory for the actuation of two-way transitions between microscopically patterned substrates, resulting in corresponding modulations of the wetting properties. Reversible switching of the surface topography is achieved through partial melting and recrystallization of a semi-crystalline polyester embossed with microscopic features. This behavior is monitored with atomic force microscopy, AFM, and contact angle measurements. The groups demonstrate that the magnitude of the contact angle variations depends on the embossment pattern.
The process of immobilizing enzymes onto solid supports for bioreactions has some compelling advantages compared to their solution-based counterpart including the facile separation of enzyme from products, elimination of enzyme autodigestion, and increased enzyme stability and activity. Researchers in the Soper Group, published in Analytical Chemistry report the immobilization of λ-exonuclease onto poly(methylmethacrylate) (PMMA) micropillars populated within a microfluidic device for the on-chip digestion of double-stranded DNA.
The group's results suggest that the efficiency for the catalysis of dsDNA digestion using λ-exonuclease, including its processivity and reaction rate, were higher when the enzyme was attached to a solid support compared to the free solution digestion. The results from this work will have important ramifications in new single-molecule DNA sequencing strategies that employ free mononucleotide identification.
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."