Honors Projects for Chemistry

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    Selenoprotein K Modulates Diverse Calcium Signaling Pathways in the Human Melanoma Cells
    (University of Hawaii at Manoa, 2018) Lee, Katie ; Hoffman, Peter R. ; Chemistry
    Store-operated calcium (Ca2+) entry (SOCE) is vital to melanoma cells for proliferation, migration, and invasion into secondary tissues. Previous work in immune cells showed that Sele-noprotein K (SELENOK) is required for efficient SOCE by palmitoylating
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    Progress in Selective Hydrogenation: Reactivity Trends in PdAu Heterogeneous Catalysts & Developing Chiral Building Blocks for New Homogeneous Catalysts
    (University of Hawaii at Manoa, 2017-05) Chinen, Amy ; Cain, Matthew ; Chemistry
    Selective hydrogenation is an essential method for converting cheap starting materials into more valuable chemical building blocks. Whether regioselectivity or diastereoselectivity is desired, catalysts are often employed to aid in this transformation. This work explores possibilities for finetuning both homogeneous and heterogeneous catalysts. Previously, bimetallic PdAu catalysts were used to enable the conversion of biologically produced 4-hydroxycoumarin (4HC) to pharmaceutically relevant coumarin and dihydroxycoumarin (DHC), but the subtleties of catalyst preparation and the effect of Pd loading were not known. Part I focuses on identifying reactivity trends resulting from variations in PdAu catalysts. Several PdAu catalysts with varying Pd:Au ratios were prepared by controlled surface reactions (CSR) or incipient wetness impregnation (IWI). Using high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GCMS), we determined the effects of the preparation method and Pd loading on reactivity, selectivity, and resistance to deactivation for the selective hydrogenation of 4HC to DHC. Part II aims to develop chiral building blocks for C1-symmetric, P-stereogenic ligands that will be used in the asymmetric hydrogenation of heavily functionalized substrates. To date, a new diastereoselective method of adding RO-H across a P=P double bond was identified and a new sterically dominating R group was generated. The results were analyzed by nuclear magnetic resonance (NMR) spectroscopy.
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    The Preparation and X-Ray Crystallographic Study of Several Ion-Exchanged, Complexed Synthetic Zeolites
    ( 1973) Kunz, Kevin Benedict ; Seff, Karl
    Zeolithic ion-exchange experiments were carried out; five ion-exchanged samples of synthetic zeolite were exchanged stoichiometrically. A successful structure determination was achieved for the hydrated zinc-exchanged zeolite, and was refined to R1 and R2 error indices of 0.097 and 0,092, respectively. The methods used for ion-exchange, zeolite complexation, and crystallographic investigation are discussed. The molecular geometries for the hydrated zinc-exchange zeolite re presented.
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    Photoprotection by Plant-derived Compounds
    (University of Hawaii at Manoa, 2014-09-26) Shelton, Hannah ; Williams, Philip ; Chemistry
    Current topical sunscreens, although effective, may not be the safest way to prevent UVradiation based skin damage. Active petroleum-derived ingredients may be toxic, and may not be the most cost-effective solution for sunscreen production. The compounds responsible for protecting plants' cellular structures from UV radiation have the potential to be an effective alternative. This project sought to determine the worth of three plant-derived compounds – lycopene, genistein, and astaxanthin – as potential sunscreen ingredients. First, SPF and Boots Star System data from in vitro UV absorption spectra were collected. Second, each compound was exposed over UV-sensitive cyantoype emulsion, in lieu of human skin, in order to determine comparative in vivo properties. While not as effective as petroleum based ingredients, these compounds showed the potential to be safe sunscreen additives, or the primary active ingredients in low SPF lotions. Additionally, the use of cyanotype emulsion was effective at determining the level of UV light permitted through a solution. Although not perfect, it has proved to be a versatile and inexpensive replacement for human skin in this experiment.
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    Misincorporation of Beta-Methylamino-L-Alanine Into Protein: A Potential Mechanism for Motor Neuron Disease
    (University of Hawaii at Manoa, 2014-09-26) Liu, Jenny ; Hemscheidt, Thomas ; Chemistry
    Imagine living in an immobilized body, while being fully aware of your surroundings. This is the experience of many motor neuron disease afflicted patients, especially those with amyotrophic lateral sclerosis (ALS). ALS-Parkinsonism Dementia complex (ALS-PDC) is a form of ALS with an abnormally high incidence in members of certain ethnicities. An ethnobotanical connection to nutrition involving the cyanobacterial neurotoxin beta- methylamino-L-alanine (BMAA) has long been postulated. Specifically, incorporation of BMAA into human protein has been suggested to contribute significantly to the etiology of ALS-PDC. Using an in-vivo approach, this research project focused on determining whether BMAA is transformed into high molecular weight substances such as proteins. The uptake and metabolic fate of BMAA was followed within a prokaryotic model system, a cyanobacterium, during the logarithmic growth phase. Prokaryotes generally have higher error rates for the misincorporation of non-proteinogenic amino acids into protein than eukaryotes. Observation of BMAA in the protein fraction would therefore provide a first estimate of the potential significance of the misincorporation of BMAA in a eukaryotic system. Chemical analysis showed that about 1% of the initial amount of BMAA added to the cell culture was present within intracellular, hydrolyzable, low molecular weight compounds below 10 kilodaltons, and only 6 × 10-4 %, if any, was present in the high molecular mass, i.e. protein, form. This suggests that intracellular protein is not a primary reservoir of BMAA in this model system and, by extension, in eukaryotes, and that an unexpectedly large percentage of BMAA, 98%, is metabolized. Imagine living in an immobilized body, while being fully aware of your surroundings.
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    Minimal nucleotide sequence divergence detected in the sea urchin Strongylocentrotus, droebachiensis by direct sequencing of enzymatically amplified DNA
    (University of Hawaii at Manoa, 2014-01-15) Stice, Ligaya ; Chemistry
    The assumptions that have been made concerning mitochondrial DNA (mtDNA) variability have been based on studies on Drosophila and vertebrates. Recent studies on marine species show marked differences in comparison to terrestrial populations. Terrestrial populations tend to show considerable amounts of mtDNA variability accompanied by distinct population structure. My study is concerned with the variation present in the mitochondrial genome of Strongylocentrotus droebachiensis populations. This sea urchin has a distribution throughout the Arctic Ocean and in both the North Pacific and the North Atlantic Oceans. Based on the previous assumptions about mtDNA variation, we should expect large degrees of sequence difference due to the mere magnitude of geographic distances involved. Using the polymerase chain reaction we have been able to determine the sequence of the ATPase 6 gene in the mitochondrial genome of six S. droebachiensis sea urchins from the North Atlantic. These sequences were compared both among themselves and to a S. droebachiensis urchin from Puget Sound, Washington. Of the approximately 1500 base pairs that were sequenced, only one base substitution was found. This indicates dramatic differences between the amounts of variation present in the sea urchin genome versus the greater diversity found in genomes previously studied.
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    Nazarov Synthesis of Cyclopentenones and Some of their Reactions
    (University of Hawaii at Manoa, 2014-01-15) Solick, Michael ; Chemistry
    During the creation of a molecular library of cyclopentenones, we discovered a new variant of the allenyl Nazarov cyclization process. The compounds that were being created for the library were β-aminoketones and epoxides that were synthesized using cyclopentenones as the precursor molecule. The precursory cyclopentenones were synthesized using the allenyl Nazarov cyclization variant developed by Dr. Tius. We wished to investigate the reactions that could be performed on these Nazarov adducts to further expand the number of compounds that may be created using the allenyl Nazarov. During the project, a new variant of the allenyl Nazarov process was discovered. The new reaction utilizes a Lewis acid, specifically ytterbium (Ill) triflate to catalyze the electrocyclic ring closure of an allenyl aryl ketone. Literature experiments similar to our reaction have shown re-aromatization of the aryl group that participates in the ring closure. Our new method yields a cyclized product in which aromaticity has been disrupted. Further experimentation and optimization of the methodology is needed, as preliminary reactions have shown poor yields (30%); however this methodology presents exciting new synthesis possibilities.
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    The Effect of the Adsorption of Substituted Phenols on the Dark and Photoconductivity of Zinc Oxide
    (University of Hawaii at Manoa, 2014-01-15) Shiigi, Stanley ; Chemistry
    One of the most active areas of present day research is in the area of heterogeneous catalysis. These studies are usually directed toward characterizing the changes which take place in the absorbate (that which is absorbed), or characterizing the changes which take place in the catalysis. The study of an absorbate on the surface of a catalysis is usually carried out using spectroscopic methods (1-3). Eischens (1) has studied the infrared spectrum of hydrogen chemisorbed on zinc oxide and has found evidence of new bands at 2.86u and 5.85u, which were proposed to be due to the oxygen-hydrogen stretching vibration of the OH group and the zinc-hydrogen stretching vibration of the ZnH or (ZnH)+ group, respectively. Zeitlin (2) has done work with o-nitrophenol adsorbed on alkaline earth oxides. A bathochromic shift in the UV maxima of o-nitrophenol was found. Terenin (3) reviews the work being done in the area of spectral studies of adsorbed molecules. The study of the changes that occur in the catalysis are being carried out by many investigators. One of the catalysis under study by these investigators is zinc oxide (4-22). Pure zinc oxide is a non-conductor; however, through various heating procedures zinc oxide may be transformed into a semiconductor that also shows varying degrees of photoconductivity. It has been shown that the electrical conductivity properties of zinc oxide is a function of the type and amount of gas molecules adsorbed on the zinc oxide surface (4,6,8,10,13,15,17). This present study attempts to characterize the effects the adsorption of substituted phenols have on the dark- and photoconductivity of pressed powder samples of zinc oxide.
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    Phosphorus-Nitrogen Dative Pi Bond Character in O, N-Dimethylhydroxylaminohalophosphines and Related Compounds
    (University of Hawaii at Manoa, 2014-01-15) Rosario, Marshal ; Chemistry
    The chloro and fluorohalophosphines of O,N-dimethylhydroxylamine were prepared and characterized by NMR and mass spectral analyses. Some conclusions as to the dative π-character of the P-N bond are drawn from the 19F NMR temperature studies and from the localization of charge in the parent ions of the mass spectra.
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    Electrochemical and Theorectical Studies of Oxidation-Reduction Reactions of Platinum (II) and (IV) Complexes
    (University of Hawaii at Manoa, 2014-01-15) Lai, Chiu-Nan ; Hubbard, Arthur ; Chemistry
    Electrochemical interconversion of complexes of Pt(II) and Pt(IV) is accelerated by the presence of halideions and halogen ligands. Semi-empirical MO Calculation and spectra data suggest that oxidation of PT(II) involves the transfer of electron density from filled orbitals of the complex, such as a1g( σ*) [5dz2] through unfilled orbitals of the compact layer or the electrode surface. Similarly, reduction of Pt(IV) complexes, for instance those of D4h symmetry such as PtIVL4X4, may proceed through interaction of a low-energy unfilled orbital if Pt(IV), such as a1g( σ*), with filled orbitals of the compact layer or the electrode surface by way of the unfilled ndz2 orbital of a bridging halide ligand. Pt(II) complexes containing unsaturated ligands such as CN­ of SCN- are less rapidly oxidized than their saturated analogs. Evidence is presented that unsaturated ligands having suitable π* orbitals stabilize the particular orbitals from which electron density is removed in the rate-limiting step. Pt(IV) complexes having a CN- ligand situated trans to a lone halide ligand are reduced with difficulty, whereas complexes having a trans-pair of halide ligands react readily; this trend is consistent with stabilization of the leaving trans-axis and de-stabilization of the interaction between the bridging ligand and the electrode surface due to d-π* back-bonding between Pt( IV) and the unsaturated ligand. A Molecular Orbital approach to the study of electrochemical reactions is presented. The calculated electrochemical rate constants are compared to experimental values obtained at thin-layer electrode. The qualitative trends agree in general. Suggestion for improvement of the calculation also included.