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The Johnson Group

The Johnson Group

The Jeff Johnson Group focuses on the development of new synthetic methods for the assembly of stereochemically complex small molecules. We are particularly interested in the design and synthesis of tailor-made reagents and catalysts for multicomponent reactions. In our recent investigations of several interesting problems, our continuing interest in the exploitation of ring strain as a source of novel reactivity led us to some mechanistically unusual heterocycle-forming cycloadditions of cyclopropanes and aldehydes. On another front, we are interested in the development of dipolar synthons for the coupling of complementary nucleophilic and electrophilic reaction partners. Our development of silyl glyoxylate reagents is an example of work in this area.

 

The Hicks Group

The Hicks Group

Research in the Hicks Group focuses on development and implementation of mass spectrometric approaches for protein characterization including post-translational modifications, as well as the identification of bioactive peptides/proteins from plants.

 

Cahoon Recognitions

Professor James Cahoon has had some very rewarding months. First, he was chosen as one of eighteen national recipients of a David and Lucile Packard Foundation Fellowship. He was elected as one of the nation's most innovative early-career scientists and engineers receiving a Packard Fellowships for Science and Engineering. Each Fellow will receive a grant of $875,000 over five years to pursue their research. "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.

James Cahoon

As if that was not enough, he was then awarded a Sloan Research Fellowship by the Alfred P. Sloan Foundation. Given annually since 1955, the fellowships go to early career scientists and scholars whose achievements and potential identify them as rising stars, the next generation of scientific leaders. "These fellowship provide a well-deserved recognition of Jim's accomplishments and will help him continue his active research program," said Valerie Ashby, Professor and Chair of the Chemistry Department. "I have no doubt that his research efforts will be the source of major breakthroughs in the field of semiconductor nanomaterials and their exciting applications."

Just the other day, we also learned that James is one of 48 recipients of an Award from the Research Corporation for Science Advancement, RCSA, which supports "innovative research projects proposed by early career scientists at American colleges and universities." The awards cover a wide range of research in astronomy, chemistry, and physics.

“RCSA has always been about finding and supporting the next big scientific paradigm, the theory or discovery that will revolutionize and advance an entire field of study,” said RCSA President Robert N. Shelton. And noted all RCSA awards are subject to a critical peer-review process, which tends ensure that funding goes to the best and brightest among America's young academic scientists, the men and women who are likely to be leaders in their fields in the coming decades. Over the past century, 40 scientists receiving RCSA support have also earned the Nobel Prize, and many others have received significant honors in the physical sciences.

Congratulations, James!!

 

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.

 

Phototherapeutics

Light-activatable drugs offer the promise of controlled release with exquisite temporal and spatial resolution. However, light-sensitive prodrugs are typically converted to their active forms using short-wavelength irradiation, which displays poor tissue penetrance. Researchers in the David Lawrence Group report in Angewandte Chemie, International Edition, on erythrocyte-mediated assembly of long-wavelength-sensitive phototherapeutics.

Research Image

The activating wavelength of the constructs is readily preassigned by using fluorophores with the desired excitation wavelength λex. Drug release from the erythrocyte carrier was confirmed by standard analytical tools and by the expected biological consequences of the liberated drugs in cell culture: methotrexate, binding to intracellular dihydrofolate reductase; colchicine, inhibition of microtubule polymerization; dexamethasone, induced nuclear migration of the glucocorticoid receptor.

 

DeSimone Awarded Dickson Prize

Dickson Prize

Congratulations to Professor Joseph DeSimone, winner of the 2014 Dickson Prize in Science, awarded annually to the person judged by Carnegie Mellon University to have made the most progress in the scientific field in the United States for the year in question. DeSimone was formally presented with the award during a February 16, 2015 ceremony where he delivered his Dickson Prize Lecture titled "Breakthroughs in Imprint Lithography and 3-D Additive Fabrication."

 

Inhalable Vaccines

Researchers at the University of North Carolina at Chapel Hill and North Carolina State University have uncovered a novel approach to creating inhalable vaccines using nanoparticles that shows promise for targeting lung-specific diseases, such as influenza, pneumonia and tuberculosis.

Cathy Fromen

The work, led by Cathy Fromen and Gregory Robbins, members of the DeSimone and Ting labs, reveals that a particle's surface charge plays a key role in eliciting immune responses in the lung. Using the Particle Replication in Nonwetting Templates, PRINT, technology invented in the DeSimone lab, Fromen and Robbins were able to specifically modify the surface charge of protein-loaded particles while avoiding disruption of other particle features, demonstrating PRINT's unique ability to modify particle attributes independently from one another.

 

Pierce Scholarship to Adrienne

Adrienne Snyder

One of thousands applicants, Adrienne Snyder, a graduate student in the Brustad Group, was selected as one of six national winner of a Thermo Scientific Pierce Scholarship. She was selected based on her essay about Engineered Transaminases. Congratulations, Adrienne!

 

 

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."