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The DeSimone Group

The DeSimone Group

Applying lithographic fabrication techniques from the computer industry, the DeSimone Group focuses on creating nanoscale particles using the PRINT©, Particle Replication in Non-wetting Templates, technology. Developed in DeSimone's lab, PRINT© enables precise control over particle features such as size, shape, chemical composition, deformability, and surface functionality. Multidisciplinary in nature, the DeSimone Group's research shows significant promise for novel applications in both life and materials science, ranging from improved vaccines to new medicines and targeted drug delivery approaches, to particulate surfactants and colloids for emerging technologies in robotics and displays.

  

The Lawrence Group

The Lawrence Group

The Lawrence Group works at the interface between organic synthesis and cell biology. In fact, half the group resides in Chemistry's Kenan Labs and the other half can be found in the newly opened multidisciplinary Genetic Medicine Building in the medical school complex. The lab focuses on the design, synthesis, characterization, and application of probes of intracellular chemistry. Research interests include new diagnostic strategies for cancer, sensors of signaling pathways, mitochondrial proteomics, the molecular basis of memory and learning, and the control of gene expression in living animals.

 

Cahoon Receives Packard Fellowship

We congratulate Assistant Professor James Cahoon as being one of eighteen national recipients of a David and Lucile Packard Foundation Fellowship. James was elected as one of the nation's most innovative early-career scientists and engineers receiving a 2014 Packard Fellowships for Science and Engineering. Each Fellow will receive a grant of $875,000 over five years to pursue their research.


James Cahoon

"The Packard Fellowships are an investment in an elite group of scientists and engineers who have demonstrated vision for the future of their fields and for the betterment of our society," said Lynn Orr, Keleen and Carlton Beal Professor at Stanford University, and Chairman of the Packard Fellowships Advisory Panel. "Through the Fellowships program, we are able to provide these talented individuals with the tools and resources they need to take risks, explore new frontiers and follow uncharted paths."

 

DeSimone in all National Academies

Chancellor's Eminent Professor of Chemistry, Joseph DeSimone, has been elected to the Institute of Medicine, one of the highest honors in the fields of health and medicine a U. S. scientist can receive. His election to Institute of Medicine represents the third time he has been named a member of a U. S. National Academy. He was elected to the National Academy of Engineering in 2005 and the National Academy of Sciences in 2012. Fewer than 20 people in history have achieved election to all three U. S. National Academies, and he is the first individual in the state of North Carolina to be named to all three U. S. National Academies.

Joseph DeSimone

"DeSimone is a renaissance scientist," said Chancellor Carol L. Folt. "He was the first to successfully adapt manufacturing techniques from the computer industry to make advances in medicine, including next-generation approaches to cancer treatment and diagnosis. He provides a beautiful example of how transcending disciplines can revolutionize science and open up entirely new fields of study. We are very proud of what Professor DeSimone and his students have accomplished. He is a gifted and talented teacher and amazing University citizen."

 

Osmolytes and Protein Crowding

In an article that not only made the cover of Protein Science, but also is a highlighted article in that issue and accompanied by an online video, then graduate student Mohona Sarkar in the Pielak Group, now a postdoc at Notre Dame University, and Professor Gary Pielak, suggest the reason why small molecules, called osmolytes, are used to overcome the effects of environmental stress.

Research Image

Osmolytes are ubiquitous in biology. Given that dehydration stress adds to the crowded nature of the cytoplasm, the team speculated that cells might use osmolytes to overcome the destabilization caused by the increased attractive interactions that accompany desiccation. They used NMR-detected amide proton exchange experiments to measure the stability of the test protein chymotrypsin inhibitor 2 under physiologically relevant crowded conditions in the presence and absence of the osmolyte glycine betaine. The osmolyte overcame the destabilizing effect of the cytosol, a result that provides a physiologically relevant explanation for the accumulation of osmolytes by dehydration-stressed cells.

 

Meyer Wins Samson Award

As announced by Israeli Prime Minister Benjamin Netanyahu on October 6th, Arey Distinguished Professor of Chemistry, Thomas Meyer, is one of two winners of the 2014 Eric and Sheila Samson Prime Minister's Prize for Innovation in Alternative Fuels for Transportation. Professor Meyer is recognized as a world leader in solar fuel research.

Professor Thomas Meyer

The $1 million prize is awarded for breakthrough work into converting solar energy into electricity capable of powering transportation. "We are making a major multi-year effort so that we will not be dependent on fluctuations in the price of oil," Netanyahu said. "This prize gives the researchers true appreciation for their efforts." The Eric and Sheila Samson Prize, totaling $1 million, is the world’s largest monetary prize awarded in the field of alternative fuels, and is granted to scientists who have made critical advancements."

Congratulations to Dr. Meyer on receiving such a prestigious international honor," said UNC Chancellor Carol L. Folt. "Dr. Meyer is a superb example of the kind of innovation we champion here at UNC, using research to solve the world's most pressing problems. By pairing a basic scientific knowledge of photosynthesis with the latest advances in nanotechnology, Dr. Meyer and his team are bringing the world closer than ever to making solar energy a practical, reliable power source."

 

Waveguide Scattering Microscopy

Dark-field microscopy, DFM, is widely used to optically image and spectroscopically analyze nanoscale objects. In a typical DFM configuration, a sample is illuminated at oblique angles and an objective lens collects light scattered by the sample at a range of lower angles. As demonstrated in an article published as the cover of ACS Photonics, researchers in the Cahoon Group have developed waveguide scattering microscopy, WSM, as an alternative technique to image and analyze photonic nanostructures. WSM uses an incoherent white-light source coupled to a dielectric slab waveguide to generate an evanescent field that illuminates objects located within several hundred nanometers of the waveguide surface.

Research Image

Using standard microscope slides or coverslips as the waveguide, the group demonstrate high-contrast dark-field imaging of nanophotonic and plasmonic structures such as Si nanowires, Au nanorods, and Ag nanoholes. Scattering spectra collected in the WSM configuration show excellent signal-to-noise with minimal background signal compared to conventional DFM. In addition, the polarization of the incident field is controlled by the direction of the propagating wave, providing a straightforward route to excite specific optical modes in anisotropic nanostructures by selecting the appropriate input wavevector. Considering the facile integration of WSM with standard microscopy equipment, the Cahoon Group scientists anticipate it will become a versatile tool for characterizing photonic nanostructures.

 

Lubrication by Polyelectrolyte Brushes

Published in Macromolecules, Professor Michael Rubinstein, in collaboration with Ekaterina Zhulina with the Institute of Macromolecular Compounds, Russian Academy of Sciences in Saint Petersburg, describe the development of a scaling model relating the friction forces between two polyelectrolyte brushes sliding over each other to the separation between grafted surfaces, number of monomers and charges per chain, grafting density of chains, and solvent quality. They demonstrate that the lateral force between brushes increases upon compression, but to a lesser extent than the normal force.

Research Image

The shear stress at larger separations is due to solvent slip layer friction. The thickness of this slip layer sharply decreases at distances on the order of undeformed brush thickness. The corresponding effective viscosity of the layer sharply increases from the solvent viscosity to a much higher value, but this increase is smaller than the jump of the normal force resulting in the drop of the friction coefficient. At stronger compression the group members predict the second sharp increase of the shear stress corresponding to interpenetration of the chains from the opposite brushes. In this regime the velocity-dependent friction coefficient between two partially interpenetrating polyelectrolyte brushes does not depend on the distance between substrates because both normal and shear forces are reciprocally proportional to the plate separation. Although lateral forces between polyelectrolyte brushes are larger than between bare surfaces, the enhancement of normal forces between opposing polyelectrolyte brushes with respect to normal forces between bare charged surfaces is much stronger resulting in lower friction coefficient. The model quantitatively demonstrates how polyelectrolyte brushes provide more effective lubrication than bare charged surfaces or neutral brushes.

 

 

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."