The Meyer Lab has a wide range of research interests based in transition metal chemistry. We have multiple ongoing collaborations with professors in both biological to physical chemistry. Members of the Meyer lab are closely involved with other groups in the Chemistry department, including Lin, Papanikolas, Templeton, Thorp, and You.
The unifying theme of our many projects is energy conversion. By studying the basic principles of electron transfer, excited states, and redox catalysis, we hope to advance the frontier of knowledge in renewable energy research. For example, we are currently investigating mechanisms of proton-coupled electron transfer, in order to understand how water is oxidized by Photosystem II during photosynthesis.
Research in the Wightman Group is directed at the development of microsensors and their use to measure chemical events in microenvironments. We have developed ultramicroelectrodes that are robust chemical sensors, which can resolve chemical events with micron or submicron spatial resolution. In addition, these probes can be used for measurements on the nanosecond time scale and in environments in which electrochemical measurements are normally impossible.
As published in Organic Letters, the Gagné Group has shown that the resting state of a gold(I)-catalyzed hydroarylation reaction changes in the presence of Ag+, with silver free catalysts resting at a dinuclear gold and Ag+ containing solutions resting at a heteronuclear gold-silver species with an asymmetric 3-center-2-electron Au-C-Ag bond stablizied by an auro-argentophilic interaction.
Adventitious Ag+, typically from LAuCl activation, can therefore intercept key organogold intermediates and effect the catalysis even when it does not effect the reaction in Au free control experiments. Key observations point to Ag+ ions intercepting Au(I) catalytic intermediates and subsequently effecting catalyst speciation and reaction kinetics; a structural model is also suggested. The discovery of dinuclear gold-silver intermediates may rationalize known Ag+ effects in gold(I) catalysis.
Carolina Chemist and John P. Barker Distinguished Professor Michael Rubinstein, has been awarded the 2010 Polymer Physics Prize from the American Physical Society. The prize recognizes outstanding contributions in polymer physics research, specifically professor Rubinstein's leadership in the field of structure and dynamics of polymer liquids, interfaces and gels.
Most of the materials around us, from plastics to tires, and inside us, DNA and proteins, are made of polymers - giant, chain-like molecules. The goal of Rubinstein’s research group is to understand how polymers move through a tangle formed by their molecule neighbors and how they are deformed if attached to each other in a network, then pulled apart, like stretching a rubber band. UNC researchers are modeling polymers in the lungs with the goal of developing treatments for diseases such as cystic fibrosis.
The unique properties of polymers that make them the materials of choice in many industries are their enormous size in comparison to ordinary molecules and their ability to change under the influence of surrounding molecules, according to Rubinstein.
Rubinstein received his bachelor’s degree from the California Institute of Technology and his master’s and doctorate degrees from Harvard University. He will be presented the award at a meeting of the American Physical Society in March 2010.
The Baer Group has published a threshold photoelectron photoion coincidence study in which the energy required to dissociatively ionize propene (C3H6 + hv → C3H5+ + H + e-) was measured to be 11.898 ± 0.024 eV. When this is combined with a recently reported ionization energy of the allyl radical, see Figure below, a high precision propene C-H bond energy (BE) as well as the proton affinity (PA) of allene could be established.
This study was complicated by the slow dissociation of the propene ion, which caused previous investigations to be too high, thereby underestimating the PA and overestimating the BE. The Baer group established the correct dissociation onset by measuring the dissociation rate constants as a function of the ion energy by time of flight mass spectrometry, and extrapolating the rate to the dissociation onset.
Researchers in the Waters Group, as published in JACS, demonstrate how phosphorylated amino acids were incorporated into a designed β-hairpin peptide to study the effect on β-hairpin structure when the phosphate group is positioned to interact with a tryptophan residue on the neighboring strand. The three commonly phosphorylated residues in biological systems, serine, threonine, and tyrosine, were studied in the same β-hairpin system.
It was found that phosporylation destabilizes the hairpin structure by approximately 1.0 kcal/mol, regardless of the type of phosphorylated residue. In contrast, destabilization due to glutamic acid was about 0.3 kcal/mol. Double mutant cycles and pH studies are consistent with a repulsive interaction as the source of destabilization. These findings demonstrate a novel mechanism by which phosphorylation may influence protein structure and function.
Joseph DeSimone, Chancellor's Eminent Professor of Chemistry at UNC, and William R. Kenan, Jr. Distinguished Professor of Chemical Engineering at NCSU, has been selected to receive this year's North Carolina Award in Science.
Considered one of the nation’s premier scientists, Joseph DeSimone was selected because of his cutting edge research with revolutionary results for cancer treatment, green chemistry and photovoltaics. His breakthroughs in nanotechnology applications and in the fields of polymer chemistry, pharmacology, and biomolecular engineering, have produced life-changing and world-saving inventions.
The North Carolina Award is the highest civilian award bestowed by the state of North Carolina, and is sometimes referred to as the "Nobel Prize of North Carolina." The awardees are chosen by the North Carolina Awards Committee, appointed by the governor of North Carolina and supervised by the state's Secretary of Cultural Resources.
Joseph DeSimone is the sixth Carolina chemist to be honored with this award. Previous Carolina recipients are Oscar Rice, 1966, Ernest Eliel, 1986, Robert Parr, 1999, Royce Murray, 2001, and Maurice Brookhart, 2008.
Protein−protein interaction is the fundamental step of biological signal transduction. Interacting proteins find each other by diffusion. To gain insight into diffusion under the crowded conditions found in cells, researchers in the Pielak Group used nuclear magnetic resonance spectroscopy (NMR) to measure the effects of solvent additives on the translational and rotational diffusion of the 7.4 kDa globular protein, chymotrypsin inhibitor 2.
The additives were glycerol and the macromolecular crowding agent, polyvinyl pyrrolidone (PVP). As published in the Journal of Physical Chemistry B, both translational diffusion and rotational diffusion decrease with increasing solution viscosity. For glycerol, the decrease obeys the Stokes−Einstein and Stokes−Einstein Debye laws. Three types of deviation are observed for PVP: the decrease in diffusion with increased viscosity is less than predicted, this negative deviation is greater for rotational diffusion, and the negative deviation increases with increasing PVP molecular weight.