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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.

 

The Miller Group

The Miller Group

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.

 

Hybrid Thermal Assembly Technique

Over the past decade, thermoplastics have been used as alternative substrates to glass and Si for microfluidic devices because of the diverse and robust fabrication protocols available for thermoplastics that can generate high production rates of the desired structures at low cost and with high replication fidelity, the extensive array of physiochemical properties they possess, and the simple surface activation strategies that can be employed to tune their surface chemistry appropriate for the intended application. While the advantages of polymer microfluidics are currently being realized, the evolution of thermoplastic-based nanofluidic devices is fraught with challenges. One challenge is assembly of the device, which consists of sealing a cover plate to the patterned fluidic substrate.

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Typically, channel collapse or substrate dissolution occurs during assembly, making the device inoperable resulting in low process yield rates. Now, in an article published in Lab on a Chip as a "Hot Article," researchers in the Soper Group report a low temperature hybrid assembly approach for the generation of functional thermoplastic nanofluidic devices with high process yield rates, >90%, and with a short total assembly time of only sixteen minutes. The functionality of the assembled devices was demonstrated by studying the stretching and translocation dynamics of dsDNA in the enclosed thermoplastic nanofluidic channels.

 

William Rand in Memoriam

A great friend of the Department, William "Bill" Rand, passed away on January 26th.

William Rand

Bill was a contributor to our chemistry department for several decades; many of you will recognize the Emmett Gladstone Rand scholarship presented at our graduation ceremony each year in memory of Bill’s father. The first recipient of this medical school scholarship? Holden Thorp! Of course Bill was a member of our Chemistry Advisory Board since day one, too, and his sense of humor and warmth were a welcome addition to any gathering.

 

Quantum Dynamics on Supercomputers

In the perspective paper published in Computing in Science and Engineering’s special topic issue on Advances in Leadership Computing, researchers in the Kanai Group and his collaborators at University of Illinois at Urbana Champaign and Lawrence Livermore National Laboratory describe the state-of-the-art computational method for simulating quantum dynamics of electrons in complex materials using supercomputers.

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They discuss a new first-principles computational method for simulating quantum dynamics of electrons in complex materials by propagating time-dependent wavefunctions. The method is designed to take advantage of a large number of processing cores in today’s supercomputers by utilizing multiple levels of different parallelization schemes. They demonstrate a strong scaling of the computational method over 1 million processing cores on an IBM supercomputer. As an example of how new material properties can be investigated using this state-of-the-art method, non-equilibrium energy transfer rate from a fast proton to the electronic excitation in bulk gold was calculated and compared to available experimental data. Importantly, the computer simulation provides detail information on how the electronic excitation is induced by the fast proton. This new first-principles quantum dynamics method enables theoretical investigations into various non-equilibrium phenomena of electrons in large complex systems.

 

Quinary Structure Modulates Protein Stability

Protein quinary interactions organize the cellular interior and its metabolism. Although the interactions stabilizing secondary, tertiary, and quaternary protein structure are well defined, details about the protein–matrix contacts that compose quinary structure remain elusive. This gap exists because proteins function in the crowded cellular environment, but are traditionally studied in simple buffered solutions.

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Researchers in the Pielak Group use NMR-detected H/D exchange to quantify quinary interactions between the B1 domain of protein G and the cytosol of Escherichia coli. In their work, published in PNAS, the group demonstrates that a surface mutation in this protein is 10-fold more destabilizing in cells than in buffer, a surprising result that firmly establishes the significance of quinary interactions. Remarkably, the energy involved in these interactions can be as large as the energies that stabilize specific protein complexes. These results will drive the critical task of implementing quinary structure into models for understanding the proteome.

 

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.

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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.

 

Charge Transfer in NaCl

The phenomenon of ion pairing in aqueous solutions is of widespread importance in chemistry and physics, and charge transfer between the ions is fundamental to understanding the behavior of aqueous ionic solutions. At the same time, it is of significant challenge to describe the charge transfer behavior using popular density functional theory, DFT, calculations in practice because of approximated exchange-correlation effects of electrons.

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In work published as a Frontiers Article and also as the cover article in Chemical Physics Letter, the group of Professor Yosuke Kanai shows how advanced quantum Monte Carlo, QMC, calculation is used to accurately quantify the charge transfer behavior in the NaCl dimer. Accurate electron density is obtained from the so-called reptation Monte Carlo approach, and influence of fermion nodes of the many-body wavefunction on the charge transfer behavior was discussed in detail. It is anticipated that the QMC approach will be of great importance for investigating a wide range of the charge transfer phenomena for which present-day DFT calculations are not reliable.

 

 

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