Using the UC Irvine Whole Air Sampler, I measured volatile organic compounds (VOCs) onboard the NASA DC-8 during the Student Airborne Research Program. High levels of the harmful chemical ozone were observed near the surface over the Sierra Nevada mountains, which led to the focus of my independent research project on the study of VOC data in order to investigate factors that contributed to ozone production. This was done by calculating the hydroxyl radical reactivity, which can, in proper conditions, be used to predict ozone formation potential. I divided the region into three boxes from east to west, based on wind direction, and the reactivity was analyzed over each region with respect to methane, non-methane alkanes, alkenes, aromatics, and biogenic compounds. In the westernmost box the reactivity was 1.7 ± 0.5 s-1 (1σ), in the middle section it was 1.4 ± 1 s-1, and in the easternmost region it was 0.8 ± 0.3 s-1. I compared the data in the Sierra Nevada region with a region known to be heavily polluted, the Los Angeles (LA) basin, and it was observed that the reactivity was 1.1 ± 0.6 s-1, lower than in two of the mountainous regions. In the Sierra Nevada mountains a major percentage of the hydroxyl radical reactivity was the result of biogenic influence, at 24% for the western box, 39% for the middle box, and 31% for the easternmost box, in contrast to only 2% biogenic contribution in LA. My work indicates that biogenic factors greatly contributed to overall ozone formation in the Sierra Nevada mountains. These mountains are strategically protected, and high pollution levels of ozone and other VOCs could lead to health impacts for visitors, vegetation, and wildlife.

Photosynthesis is how plants gather energy from the sun and store it as chemical energy. This pathway involves multiple energy gathering antennae that absorb light and move electrons through photosystems to store the energy in NADPH and ATP and in turn split water into O₂ and 2H₂. There are two mechanisms proposed for the O-O bond forming step catalyzed by the oxygen evolving complex (OEC), Mn^dang-CaMn₃O₅, of photosystem II, and the dangling Mn (Mn^dang) and Ca ions have both been shown to be involved. One mechanism is through nucleophilic attack by an OH^- that is coordinated to the Ca ion at an electrophilic Mn(V)≡O species, and the other is through radical coupling between two Mn(IV)-O• species. Recent data shows that the nucleophilic attack mechanism is the most likely mechanism. Because the O-O bond forming step occurs after the rate-determining step, these intermediates are not observable in photosystem II. This project involves the synthesis and isolation of species that are representative of the Mn^dang-O-Ca fragment, and intermediates involved in one of the proposed mechanisms for O-O bond formation by the OEC. We are using [Mn(II)(N₃S^Me2(tren))]⁺ as our Mn starting material, and [(dipp-DAD)Ca²⁺(OH)₂]^2- as Ca-(OH)₂ source. The reaction between these two compounds will be monitored by UV-Vis, in the presence of an oxidant, to detect changes in the Mn ion’s electronic environment. So far we have been able to isolate the previously reported [(dipp-DAD)Ca²⁺(THF)₃] precursor complex, and our next step will be to generate hydroxide derivative and monitor its reaction with [Mn(II)(N₃S^Me2(tren))]⁺ using the method described above.

Ionic liquids (ILs) are well known to cause a range of interesting effects on proteins and enzymes. However, there is still much to be done to understand the molecular scale mechanisms of these processes. Using molecular dynamics (MD), we have studied how several IL solutions change the structure and behavior of two short, model, Leucine-Lysine (LK) composed peptides at a hydrophobic interface. These peptides - LKalpha14 and LKbeta15 - have been researched extensively through experiment and simulations in water, but have not yet been examined when exposed to ILs. In our study we found that the two 50% 1-Butyl-3-methylimidazolium solutions we tested had a substantial effect on both the secondary structure and surface affinity of our peptides when compared to water. IL solutions reduced the adsorption affinity of both LKalpha14 and LKbeta15 for the interface, while also preventing LKbeta15 from forming extended beta sheet structures. In place of these beta sheet structures, we observed the formation of a L-alpha-like helix for lone LKbeta15 peptides at the interface. IL presence also had a subtle effect on LKalpha14’s strong alpha helical character, reducing it for interface bound peptides and increasing it for peptides in bulk solution. This work provides several new testable hypothesis about IL action on biomolecule structure that can be studied in detail using surface techniques such as sum frequency generation (SFG) spectroscopy.

The diffusion of ions into a nano-scale ZnO lattice has gained attention in the past decade as a possible solution to the rapid fracturing of ZnO electrodes in bulk batteries and as an alternative to conventional LiCoO₂ and LiFePO₄ materials which are expensive to manufacture and environmentally hazardous. Experiments have shown that utilizing bulk (ie. not nano-structured) ZnO electrodes fracture in discrete segments (a leapfrog effect) after only a few charge/discharge cycles, diminishing the effective charging/discharging capacity. Current efforts are aimed at using nano-scale lattices which fall within the size range of the cracking separations and thus are not susceptible to leapfrog fracturing. Using an optimized quantum dot structure and conventional ab initio electron structure theory methods, the effects of lithium ion intercalation into a Zn₃₃O₃₃ quantum dot lattice were investigated. The main research questions were: (1) where are the potential energy valleys in which lithium ions can settle; (2) What effect does lattice expansion have on the energy of a lithium-ion charged quantum dot; and (3) how does doping the dot with iron affect the energy? Using a rigid and a relaxed scan of a lithium entering and exiting through the C3v axis of the quantum dot, the potential energy landscape was mapped, illustrating the presence of multiple potential valleys in which ions could settle. We used single point calculations to determine the optimal expansion factor after observing expansion in previous molecular dynamics simulations. Currently preliminary results indicate a possible trend regarding iron positioning within the lattice and we hope to improve our data by introducing a larger Zn₈₄O₈₄ dot. Hopefully our findings will demonstrate that nano-scale iron doped ZnO lattices are not subject to leapfrog fracturing and may therefore be cheap and viable options as battery electrodes.

All biological systems are dependent on properly folded protein molecules to function correctly. To enable major developments in biotechnology and medicine, an understanding of the protein folding process is needed. Advances in this field have been made, however most of the knowledge gained has been concentrated on structured beta-sheets and alpha-helices. Experimental studies of beta-strand association and the effects of conformational dynamics in unstructured loop regions remain scarce, in part because the timescales of the dynamics leave few spectroscopic methods available for measuring kinetics. Using a model system consisting of two beta-strands connected by a loop of variable length and composition, measurements of beta-strand association dynamics on microsecond to millisecond timescales have been made by employing Relaxation Dispersion Nuclear Magnetic Resonance (NMR) techniques. In addition, using multidimensional NMR and Circular Dichroism spectroscopy, sequence-specific thermodynamic effects in the folding of these peptides have been examined. Loop closure was originally thought to be so fast that it would be negligible in the protein folding process, however our measurements show that loop closure rates can vary significantly depending on size and composition. Peptides containing all-glycine loops of length 3 – 16 have been shown to have folding rate constants (1/kf) of 12.3 – 109 microseconds with unfolding rate constants (1/ku) of 636 – 191 microseconds at 300 Kelvin. Insertion of structured beta-turns into the loop region were shown to increase the rate of folding, from 231 microseconds for an all glycine 10-loop to 25.0 microseconds for a length-10 loop containing an organized turn. These measurements have shown that the interplay of conformational entropy and residual segmental motion are crucial to understanding the stability and dynamics of beta-sheets. Current and future work on this project seeks to understand how tuning the dynamics of beta-sheets will affect thermodynamics and kinetics of ligand binding in biologically relevant systems.

Alkanes, or saturated hydrocarbons, are the major constituents of natural gas and petroleum. Conversion of the chemically inert bonds of alkanes to more useful functional groups (like alcohols, aldehydes, and carboxylic acids) requires a great deal of energy and is often expensive. For this reason, functionality is often added using olefin precursors, or unsaturated hydrocarbons. Thus, more efficient and cost-effective conversions of alkanes to olefins, or alkane dehydrogenation, are highly desirable. Prior work shows alkane dehydrogenation may be achieved with iridium and rhodium pincer complexes. While significant success in this type of alkane functionalization has been achieved with Ir^I systems, these C–H bond-activating systems are inhibited by nitrogen and water, and can be self-inhibited by olefins. In contrast, Ir^III complexes have been shown to be tolerant to these inhibitors and are able to activate the C–H bonds of alkanes. Our experimental and computational results show usage of Brønsted acids to generate new Ir^III systems, in particular (^dmPhebox)Ir(OAc)(X) complexes, leads to an increase in the rate of C-H activation over the previously reported (^dmPhebox)Ir(OAc)₂(OH₂) system. The product of this activation and dehydrogenation reaction is olefin and (^dmPhebox)Ir(OAc)(H). Optimized conditions for this alkane dehydrogenation system and mechanistic studies will be presented.