University of Minnesota
University of Minnesota

Go to chemistry home page.


Eight graduate students receive Doctoral Dissertation Fellowships

Eight of the Department of Chemistry's top doctorate students have received 2013-14 Doctoral Dissertation Fellowship (DDF) program awards. Recipients include Makenzie Provorse, who is advised by Jiali Gao; Gregory Rohde, who is advised by Professor Lawrence Que Jr; Paul "Alex" Rudd, who is advised by Professor Connie Lu; Stephen Rudisill, who is advised by Professor Andreas Stein; Stephen Tereniak, who is advised by Professor Connie Lu; Kelly Volp, who is advised by Professor Andrew Harned; Yen-Chih Wang, who is advised by Professor Mark Distefano, and Xu Zou, who is advised by Professor Philippe Buhlmann.

The Doctoral Dissertation Fellowship program is a university-wide competition that supports top doctorate students in their final year of study. This year, 151 awards were made. Awardees receive an academic year stipend of $22,500, participate in a monthly seminar series, present their research at an annual poster session, and receive travel grants to present their work at a national or international conference.

Makenzie Provorse is entering her fifth year of graduate school and has been conducting research under the supervision of Professor Jiali Gao. Makenzie's research focuses on theoretical and computational investigations of proton-coupled electron transfer (PCET) reactions, in both chemical and biological systems. Although there are models for PCET using empirical potential energy functions, called molecular mechanics, there was no practical method based on quantum mechanical approaches for modeling PCET in condensed phase simulations. Makenzie's work involves the development and validation of a novel multiconfigurational, multistate density functional theory (MSDFT) such that the electron and proton localized electronic configurations can be accurately modeled. This method goes beyond the traditional Kohn-Sham DFT and can be used to understand the mechanism of a variety of artificial and natural processes involved in energy conversion, including singlet fission of nanomaterials and PCET of organic dyes. Makenzie is currently applying the MSDFT method, implemented into the program CHARMM, to understand the free-radical propagation pathway of ribonucleotide reductase, in which a tyrosyl radical tunnels over a distance of more than 35 angstroms through a sequence of PCET hops.

Gregory Rohde is conducting research under the direction of Professor Lawrence Que Jr., and is studying synthetic model complexes of iron- containing enzymes. These enzymes perform a vast array of transformations including the conversion of methane to methanol using atmospheric oxygen. Nature has evolved these efficient reaction centers with environmentally friendly and abundant iron. Chemists are now just starting to utilize similar chemistry with iron to carry out interesting catalytic transformations, which are historically performed by toxic and expensive metals. Currently, Gregory is investigating factors contributing to the reactivity of the synthetic models, as well as understanding how these iron centers activate oxygen. The discoveries made with the model complexes will be applied to improve nonheme iron biocatalysts modeled after the enzymes. As part of his graduate work, Gregory travels to the Stanford Synchrotron Radiation Lightsource (CA) and Brookhaven National Lab (NY) to perform X-ray absorption experiments to study the properties of the iron systems from the Que lab.

Paul "Alex" Rudd is entering his fifth year of graduate school and has been conducting research under the supervision of Professor Connie Lu. Work in the Lu laboratory is focused on understanding the electronic structure of metal-metal bonds. By generating a library of bimetallic complexes, the individual contributions of each metal to the metal-metal bond can be elucidated, and these effects are ultimately hoped to guide efforts in multi-electron redox catalysis. One of Alex's current projects involves iron-alane complexes, which are shown to reduce dinitrogen by four electrons to generate a silylhydrazido derivative; the initial iron complex is an unusual negative oxidation state, Fe(1-), which is stabilized by the alane. Another project involves study of the covalent multiple bonds between chromium and iron, which represent the first example of multiple bonds between different first row transition metals. This complex is shown to mediate two-electron reduction of carbon dioxide to potassium oxalate, which is the ongoing subject of both catalytic and mechanistic studies. Alex is also interested in metal-ligand multiple bonds, spectroscopic investigations of reactive complexes, and interdisciplinary work between chemistry and materials science.

Stephen Rudisill is entering his fifth year of graduate school, and is advised by Professor Andreas Stein. His research thus far has focused on using aqueous sol-gel chemistry to influence and generate nano-to-microscale structures in a variety of materials. Recently, he has been working to generalize a method of producing three dimensionally ordered macroporous microspheres via the Pechini method. In this process, metal ions are combined with citric acid to form complexes, and then those complexes are linked together by ethylene glycol, forming a metal-laced polymer. The electrostatic interactions of this developing polymer with an array of poly(methyl methacrylate) spheres govern the formation of microscale structures throughout the template. Stephen also studies thermochemical cycling of macroporous materials for water-splitting and the structural organization of collagen fibrils in aqueous solution, with the eventual goal of producing inexpensive artificial corneas.

Stephen Tereniak will be starting his fifth year of graduate school in the fall of 2013 semester under the guidance of Professor Connie Lu. His research interests include the synthesis, characterization, and reactivity of metal-metal bonded bimetallic compounds. Until recently, few examples of metal-metal bonded bimetallics had been prepared involving mid-to-late first-row transition metals such as manganese, iron, and cobalt. Metal-metal bonded heterobimetallics with these elements (such as iron-manganese) were unknown. Bimetallics containing these elements are interesting because the metal-metal bonding gives properties that could facilitate new kinds of reactivity, and the elements themselves are found in bimetallic enzymes that catalyze difficult transformations such as the selective oxidation of methane to methanol. Steve has prepared and characterized an isostructural series of bimetallics with the pairs cobalt-cobalt, cobalt-iron, cobalt-manganese, iron-iron, and iron-manganese. With these bimetallics in hand, Steve is now investigating their reactivity towards small molecules such as dioxygen with an eye towards oxidizing substrates, e.g. alkenes to epoxides. Aside from oxidation chemistry, Steve is also interested in other transformations of general societal importance, including the conversion of dinitrogen to ammonia, carbon dioxide to alternative fuels such as methanol, and water oxidation.

Kelly Volp is entering her last year of graduate school, conducting research under the tutelage of Professor Andrew Harned. Her research interests are motivated by the synthesis and methodology of cyclohexadienones. One of her current projects is developing novel chiral aryl iodide catalysts for the dearomatization of phenols to access chiral para-quinols. These small molecule building blocks can then be applied in the synthesis of complex molecules and natural products. Other research projects include investigating the origin of unexpected stereoselectivity during alkylation of malonate-derived bicyclic lactones, which was first observed during the total synthesis of the polyketide sorbillactone A. The ultimate goal of this research is to develop new asymmetric reactions and gain a better understanding of stereoselectivity in order to efficiently synthesize molecules that can be used in the construction of biologically active natural products. Kelly is also involved in the Joint Safety Team, aimed at improving the culture of safety in chemical laboratories at the University of Minnesota.

Yen-Chih Wang is entering his 6th year of graduate school, conducting research under the guidance of Professor Mark Distefano. His research focuses on studying substrate specificity of an enzyme called protein farnesyltransferase (PFTase). Farnesylation which is catalyzed by this enzyme is required for the proper function of many proteins involving in different medical conditions. He has synthesized peptide arrays to screen PFTase to probe its specificity. In contrast to the standard solid-phase peptide synthesis, the peptide arrays he made have peptides with free C-termini. His peptide-array screening is faster and more efficient than the conventional methodology. Now he is comparing the substrate specificity of PFTases from different organisms. Because PFTase uses two different substrates, he is also studying the structural influence between these two substrates by his screening methodology. Yen-Chih is also studying the reaction and specificity of a membrane protease which is involved in the subsequent processing of farnesylated proteins in cells. The ultimate goal is to provide insights for development of novel pharmaceuticals. The results may also reflect mechanisms for regulating farnesylation with impact on the localization, trafficking, and activity of farnesylated proteins within cells.

Xu Zou is advised by Professor Philippe Buhlmann and will be entering his 5th year of graduate study, where he designs and constructs electrochemical sensors for clinical, environmental, and chemical process analysis. Xu's research focuses on developing two components in an ion-selective electrode system: calibration free solid contact electrode and liquid junction free reference electrode. Xu is particularly interested in developing a universal method in solid contact electrode by including redox couples into the solid contact layer which acts as both a transducer layer and a potential buffer layer to provide stable, reproducible and reliable signals. Xu is also aiming to eliminate liquid junction in reference electrode. The vast majority of all electro-analytical measurements are performed versus reference electrodes with liquid junction which suffer from clogging and contaminations in real samples, and requires replenishing and flushing frequently. Xu's work involves the application of a current pulse to a hydrophobic ion-doped membrane, thereby controlling transmembrane ion fluxes to obtain a liquid junction free and maintenance free reference electrode. The ultimate goal of his research is to develop miniaturized electrochemical sensors for portable and implantable devices.