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  • Undergraduate Poster Abstracts
  • Chemical Engineering

    FRI-726 OPTIMIZATION OF PROTEIN SECRETION PURITY IN SALMONELLA BY TYPE III SECRETION

    • Michelle Reid ;
    • Kevin Metcalf ;
    • Danielle Tullman-Ercek ;

    FRI-726

    OPTIMIZATION OF PROTEIN SECRETION PURITY IN SALMONELLA BY TYPE III SECRETION

    Michelle Reid, Kevin Metcalf, Danielle Tullman-Ercek.

    University of California, Berkeley, Berkeley, CA.

    Large quantities of highly purified protein are required for biotechnological application, structural and functional characterization, and therapeutic purposes. Heterologous proteins are susceptible to proteolytic degradation, aggregation, and incomplete translation in the host. This necessitates the use of a specialized system, capable of targeting any protein of interest (POI) and exporting it out of the cell. Salmonella enterica, like other Gram-negative bacteria, possess the type III secretion system (T3SS): a protein pump apparatus that can export proteins from the cell in one step, bypassing both inner and outer membranes. Although secretion through the T3SS is highly specific, harvested culture media containing the POI also show a presence of cosecreted, flagellar, T3SS virulence proteins. We hypothesize that the deletion of native virulence effectors and secreted flagellar proteins in S. enterica will enhance the purity of T3SS-secreted heterologous proteins. We employ recombineering methods to eliminate these genes. After the progressive elimination of the aforementioned genes, secretion and expression levels are visualized by Coomassie staining and quantified by western blot. Our results will further our efforts toward creating a strain for highly specific export of heterologous proteins at levels meeting industrial demand.

    FRI-724 SODIUM NICKEL MANGANESE OXIDE AS A POTENTIAL CATHODE MATERIAL FOR SODIUM-ION BATTERIES

    • Moses Kodur ;
    • Chuze Ma ;
    • Shirley Meng ;

    FRI-724

    SODIUM NICKEL MANGANESE OXIDE AS A POTENTIAL CATHODE MATERIAL FOR SODIUM-ION BATTERIES

    Moses Kodur, Chuze Ma, Shirley Meng.

    University of California, San Diego, La Jolla, CA.

    Because of the need for low-cost energy-storage devices, sodium-ion batteries are being investigated as potential candidates due to the abundance of sodium and its chemical similarity to lithium. In the many studies conducted on layered cathode materials for sodium-ion batteries, relatively low reversibility and poor rate performance have been exhibited. In this project, a morphology controlled Na0.78Ni0.23Mn0.69O2 is investigated as a potential cathode material. Solid state synthesis is used to make the material. Purity is confirmed through X-ray diffraction. When tested from 2.0 V to 4.5 V, the material exhibits a specific capacity of 135 mAh/g at a current density of 12 mA/g. The capacity can still be maintained as high as 120 mAh/g despite increasing the current by 50 times (600 mA/g). This is, so far, the best performance rate of layered oxide cathodes for sodium-ion batteries. Therefore, a series of material characterizations including X-ray absorption spectroscopy, scanning transmission electron microscopy, and electron energy loss spectroscopy are ongoing in order to reveal the Na intercalation mechanism of the internal redox reaction, as it is yet unknown.

    THU-724 ANALYZING FATIGUE DUE TO CYCLIC LOADING IN POLY(3-ALKYLTHIOPHENE)-THIN FILMS WITH THE WEAKLY INTERACTING H-AGGREGATE MODEL

    • Shang-Chun Chiang ;
    • Adam Printz ;
    • Darren Lipomi ;

    THU-724

    ANALYZING FATIGUE DUE TO CYCLIC LOADING IN POLY(3-ALKYLTHIOPHENE)-THIN FILMS WITH THE WEAKLY INTERACTING H-AGGREGATE MODEL

    Shang-Chun Chiang, Adam Printz, Darren Lipomi.

    University of California, San Diego, La Jolla, CA.

    Organic semiconductors are promising materials for applications that require mechanical compliance and robustness such as wearable and implantable biomedical devices and stretchable organic photovoltaics. However, even highly compliant devices experience failure when repetitively strained. This failure (or fatigue), which is likely due to disruption in the quantity and quality of polymer aggregates that dominate charge transport in poly(3-alkylthiophene)s, can be measured using UV-vis spectroscopy and the weakly interacting H-aggregate model. The polymer films were transferred to stretchable substrates, strained cyclically, and measured periodically to determine the quantity and quality of high-charge transport aggregates. Preliminary data showed a critical number of cycles dependent on the strain percentage before the destruction of polymer aggregates began to occur. Understanding the degradation mechanisms and loading limits of conjugated polymer films undergoing cyclic strain will inform scientists and engineers and allow for the intelligent design and selection of polymers for applications requiring repetitive strains such as portable and wearable stretchable or flexible electronic devices.

    FRI-725 SUSTAINABLE PRODUCTION OF BIOFUEL FROM LIGNOCELLULOSIC BIOMASS USING ZEOLITE CATALYSTS

    • Syed Hussain ;
    • Wei Fan ;

    FRI-725

    SUSTAINABLE PRODUCTION OF BIOFUEL FROM LIGNOCELLULOSIC BIOMASS USING ZEOLITE CATALYSTS

    Syed Hussain1, Wei Fan2.

    1Lone Star College, The Woodlands, TX, 2University of Massachusetts, Amherst, Amherst, MA.

    Biofuels have been proposed as an alternative to fossil fuel due to environmental concerns, but clearing forest, grasslands, and wetlands to produce food-crop-based biofuel only contributes to carbon emission. Developing a sustainable and productive process to convert lignocellulosic biomass from agricultural, yard, and forest residue to biofuel will provide a great carbon-neutral energy source. Bio-oil transformed from this biomass can further be upgraded to long hydrocarbon chains using the aldol condensation reaction of acetone and furfural in the presence of a catalyst. Heterogeneous catalysts such as zeolite have proven to be very successful in the petrochemical industry. Therefore, we investigated 3 different types of zeolites based on their compounds and structural framework to determine the best catalyst for this reaction. Our experimental analysis on the reactivity of these zeolites using gas chromatography revealed that tin-based zeolites with BEA framework (Sn-BEA) gave the greatest conversion rate, high turnover frequency, and low activation energy. However, product selectivity in Sn-BEA decreased with time as compared to other specimens. Our results suggest that, due to the high reactivity, dimerization of the desired product is occurring. Our goal is to understand how different compounds and pore sizes in zeolites affect the reaction system and to suggest the characteristics of a better zeolite for future synthesis. Therefore, a more thorough study on Sn-BEA zeolites is needed to understand the dependant variables in the process in order to achieve a greater product yield.

    THU-725 ENGINEERING SIGNAL SEQUENCES ON THE N-TERMINUS OF SALMONELLA ENTERICA: 1,2-PROPANEDIOL UTILIZATION MICROCOMPARTMENT PROTEINS

    • Kamaria Kermah ;
    • Christopher Jakobson ;
    • Danielle Tullman-Ercek ;

    THU-725

    ENGINEERING SIGNAL SEQUENCES ON THE N-TERMINUS OF SALMONELLA ENTERICA: 1,2-PROPANEDIOL UTILIZATION MICROCOMPARTMENT PROTEINS

    Kamaria Kermah1, Christopher Jakobson2, Danielle Tullman-Ercek2.

    1El Camino College, Torrance, CA, 2University of California, Berkeley, Berkeley, CA.

    The Pdu (1,2-propanediol utilization) microcompartment is a complex protein chamber that encases a specialized metabolic pathway that Salmonella enterica uses for its pathogenicity in the human gut. This unique packaging system can be effectively engineered for industrial use as a nanobioreactor or molecule transporter. Pdu microcompartments localize diol dehydratase (PduCDE), an enzyme complex encoded by the pduCDE genes. This enzyme complex contains a signal sequence on the PduD protein that promotes encapsulation. The N-terminal of the PduD protein contains a hydrophobic motif that serves as signal sequences that localizes diol dehydratase. The variability of this hydrophobic pattern is of importance in engineering microcompartments. Through homologous recombination, numerous signal sequences with corresponding hydrophobic faces were engineered into the 5´ end of pduD genes. Cells were grown simultaneously and selected on 1,2-propanediol-infused media. The growth rate of the cells will be compared to that of wild-type Salmonella enterica cells by optical densities. By assessing the surviving cell’s genome, we will clarify the role of protein patterns in localization. This information can be used for engineering synthetic microcompartments to produce biofuels, clean forms of energy, and chemicals of interest.

    THU-723 TWO-STEP PASSIVATION OF IN0.53GA0.47AS USING 1-EICOSANETHIOL AND AMMONIUM SULFIDE

    • Adrian Acosta ;
    • Yissel Contreras ;
    • Stacy Heslop ;
    • Anthony Muscat ;

    THU-723

    TWO-STEP PASSIVATION OF IN0.53GA0.47AS USING 1-EICOSANETHIOL AND AMMONIUM SULFIDE

    Adrian Acosta, Yissel Contreras, Stacy Heslop, Anthony Muscat.

    The University of Arizona, Tucson, AZ.

    The development of faster, more efficient electronic devices using III-V semiconductors requires surface passivation processes to protect against oxidation and electrical degradation due to the presence of surface states. A 2-step, liquid-phase surface passivation of the (100) crystal plane of In0.53Ga0.47As with 1-eicosanethiol (ET, 20 carbon atom chain) and ammonium sulfide, (NH4)2S, was investigated using X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry, and water contact angle. The time required to reoxidize the clean surface of InGaAs samples when exposed to air depended on the order of the passivation steps. The InGaAs substrates were initially cleaned with dilute aqueous HF to remove the native oxides. Immersing a sample first in 3 mM aqueous (NH4)2S for 20 min followed by 4 mM ET dissolved in ethanol for 20 min did not protect the surface for exposures as short as 4 min. Reversing the steps and immersing first in ET followed by (NH4)2S prevented oxides from growing for up to 8 min due to reaction with oxygen and water in the air. When ET was deposited first, ellipsometry showed that the overlayer thickness of 41.4 ± 5.6 Å was well above the 26.9 Å length of an ET molecule and the water contact angle of 106.8° ± 1.1º showed a hydrophobic surface confirming deposition of at least one ET layer. In comparison, a single 20 h immersion in 4 mM ET protected the surface from oxidation for only 4 min. A 2-step passivation procedure can offer a significant improvement in the surface passivation of III-V semiconductors.

    THU-726 ELECTROCATALYSTS FOR OXYGEN REDUCTION FROM IRON AND SMALL MOLECULE ORGANIC PRECURSORS

    • Jonathan Gordon ;
    • Alexey Serov ;
    • Plamen Atanassov ;

    THU-726

    ELECTROCATALYSTS FOR OXYGEN REDUCTION FROM IRON AND SMALL MOLECULE ORGANIC PRECURSORS

    Jonathan Gordon, Alexey Serov, Plamen Atanassov.

    The University of New Mexico, Albuquerque, NM.

    Fuel cells are a clean and highly efficient means of harnessing energy from chemical reactions in the form of electricity. All fuel cells require catalysts to increase the rate of electron transfer on the surface of the electrodes. In hydrogen fuel cells, the most effective catalysts are composed of platinum (Pt) and Pt-based alloys, the high cost of which impedes large scale implementation. In this study, we aim to synthesize catalysts for the oxygen reduction reactions (ORR), which take place at the cathode of hydrogen fuel cells, from small, inexpensive nitrogen-containing organic molecules and Fe to overcome this hurdle. All catalysts were prepared using the sacrificial silica support method developed in our research group. In this method, precursor materials are templated onto silica supports and subjected to high temperature pyrolysis. The silica support is then removed by acid leaching in hydrogen flouride (HF) to yield highly porous nitrogen-doped carbon matrices with high surface areas rich in Fe-Nx/C catalytic active sites as revealed by SEM, BET, and XPS analyses, respectively. Catalytic activity for ORR was measured in acidic (0.5 M H2SO4) and alkaline (1 M KOH) media using the RRDE method and in fuel cell tests. XRD data for Fe indicates that small, on the order of several nanometers, metallic iron particles exist. We assume that the homogeneous distribution of precursors on the surface of fumed silica prevents metal particle agglomeration. Presented here are the results of these experiments with a particular emphasis on identifying promising precursors worthy of further optimization and implementation.

    FRI-727 COST-EFFECTIVE ION-SELECTIVE ELECTRODES FROM METAL-AZO COMPLEXES

    • Warren Nanney ;
    • Kenneth Rodriguez ;

    FRI-727

    COST-EFFECTIVE ION-SELECTIVE ELECTRODES FROM METAL-AZO COMPLEXES

    Warren Nanney, Kenneth Rodriguez.

    California State University, Dominguez Hills, Carson, CA.

    Ion selective electrodes (ISE) are used regularly in analytical chemistry to determine concentration of ions in solutions. These electrodes, however, are either too expensive ($500+ per unit) or too complex to develop for a classroom-level laboratory experiment. We have developed techniques reducing the cost and complexity of designing and performing classroom laboratory ISE experiments. These experiments involved not only reducing costs of the electrodes themselves, but also reducing the costs of the metering equipment required in a classroom setting. The ISEs created were a membrane type using Ca2+, Mg2+, and Cu2+ ions complexed with either 2,2′-(ethanediylidenedinitrilo)diphenol (GBHA) or 4-(4-nitrophenylazo)resorcinol (Azo Violet), then homogeneously mixed into a thin layer of plasticized PVC. The success of each electrode was determined first by calibration, then by measurement of a separate unknown standardized solution. The electrode was also tested for interference by taking measurements of solutions with possible interfering ions. Measurements were also taken on different meters to verify the accuracy of the less expensive meters. A small cohort of quantitative analysis student volunteers successfully executed a draft ion selective electrode experiment based on this research.