2008 Capstone Celebration Symposium
PLU Chemistry Department
May 2nd to May 6th, 2008
Come and join the chemistry department to hear the senior capstone presentations. Student presentations will occur Thursday and Friday. The schedule of talks with more details is given below.
All talks will be held in the Morken Center in Room 103!
1:45 pm - Synthesis of Gold Nanoparticle Aggregates for use as SERS Microscopy Substrates
Jeffrey Ebel, Senior Capstone Seminar
Solutions of sulfate-stabilized gold nanoparticles (GNP’s) were synthesized based on variations to the methods of Davis et al. in an attempt to produce monodisperse preparations of small (~20nm), spherical, SERS-active nanoparticles for future detection of biological molecules such as Erythropoietin. Altogether, over 100 variations to the Davis method were performed, including potential SERS active green approaches, to formulate specialized GNP’s in a reproducible fashion. The key factors for producing small monodisperse GNP’s resulted from the amount and timing of the gold solution (HAuCl4) injections. Optimal results were achieved from the smallest aliquot additions, twenty 50 μL injections, of 0.1 HAuCl4 solution as confirmed by UV-Vis, DLS, SAXS, TEM, and AFM. The GNP’s synthesized also exhibited the ability to be bound to a glass surface functionalized by either APTMS (3-aminopropyltrimethoxysilane) or APTES (3-aminopropyltriethoxysilane). AFM images of these slides displayed evidence of successful binding of the GNP’s to the surface and a future for gold monolayer SERS microscopy detection.
2:25 pm - Analysis of Arboreal Microbial Peptides by Tandem Mass Spectrometry
Kimberly Cotten, Senior Capstone Seminar
As access to the canopy of temperate forests increases, new techniques are being used to study the flora and fauna found there. The bacteria of these habitats have received relatively little study; thus I explored the use of a commonly-used proteomics technique to examine these soils for bacterial or other biomarkers. Tandem mass spectrometry was used to identify proteins found in soil samples to differentiate between floor and soil microbial communities. However, the technique proved difficult to apply to these samples because of the contaminants that interfere in the separation and ionization of peptides in the mass spectrometer, and the lack of a complete proteomic database against which to search the resulting protein sequences.
3:05 pm - 10 Minute Break - Senior Photograph
3:15 pm - Effect of Microbial Metabolites Pyruvic and Lactic Acid on the Dissolution Rate of Hydroxyapatite
Dianna Manjarrez, Senior Capstone Seminar
In order to quantify the effect of environmental factors such as pH and temperature on the dissolution of hydroxyapatite, the conditions affording the maximum release rate, or forward rate, must first be established. The effect of the microbial metabolites L-lactic and pyruvic acid, in a buffer solution of TRIS [tris(hydroxymethyl)aminomethane], on the dissolution rate of hydroxyapatite at a temperature of 60C and a pH of 7, was quantified as a function of the ratio of flow rate to surface area (q/S). The single-pass-flow-through (SPFT) method was used and the aqueous effluent samples collected were analyzed for calcium and phosphorous using inductively couples plasma-optical emission spectroscopy (ICP-OES). The forward rate for hydroxyapatite as indexes by Ca and P in the presence of pyruvic acid were found to be 9.14 ± 0.9 x 10-11 (mol m-2 s-1) at log10 (q/S) = -8.75, and 1.1 ± 0.1x 10-10 (mol m-2 s-1) at log10 (q/S) = -8.76 respectively. The forward rate of dissolution for hydroxyapatite in the presence of lactic acid was confounded by secondary precipitation and is under further investigation.
12:30 pm - Inverse Electron Demand Diels-Alder Reactions of Terminally-Activated Dienes
Chelsea Berdahl, Senior Capstone Seminar
Inverse electron demand (IED) Diels-Alder reactions between alkene dienophiles and dienes bearing terminal electron-withdrawing groups are reported in only scattered accounts. While proven to be less reactive than dienes bearing withdrawing substituents at an internal position, the synthetic utility of terminally-activated dienes under Lewis acidic conditions has not been examined systematically. Two parent aldehyde substrates, (2E,4E)-2,4,9-decatrienal and (2E,4E)-2,4,10-undecatrienal, have been targeted to investigate IED intramolecular Diels-Alder reactions under thermal and Lewis acid conditions. The latter substrate has been successfully synthesized in 10% yield over four unoptimized steps from commercially-available 7-octen-1,2-diol. While the thermal reaction of (2E,4E)-1,4 10-undecatrienal proceeds between 170 °C-200 °C (toluene, sealed tube) in low yield, a screen of Lewis acids indicates that methylaluminum dichloride promotes reaction at 25 °C.
1:10 pm - The Role of Tannins in the Aging of Red Wines
William Goldsworth, Senior Capstone Seminar
Tannins are polyphenolic compounds found in wine that form complexes with proteins. Polyphenols have been studied and shown to provide antioxidant and detoxifying effects as well as inhibiting and decreasing colony formation of melanogenic activity. Tannins are responsible for the astringency and the long-term color stability of red wines. There is a desire in the wine community to exploit the properties of tannin to improve current wine making techniques and provide more predictability in aged red wines. Some of the current methods of research for quantitative analysis of tannins included in this work are Fourier transformed mid-infrared (FT-MIR) spectroscopy and an electronic panel based on the combination of an electronic nose, an electronic tongue and an electronic eye. These methods have shown promise in targeting tannins in red wines and are a step towards understanding the aging process of red wines.
1:50 pm - Antimicrobial Properties of Bark and Root Extracts from Native Ribes species
Kelly King, Senior Capstone Seminar
A selection of the Ribes genus gooseberry/currant plants native to the Northwest were targeted to extract, isolate, and identify antimicrobial compounds based on ethnobotanical literature. Air-dried roots and stems of R. divaricatum, R. aureum, R. bracteosum, and R. Sanguineum were washed with refluxing petroleum ether and then extracted with methanol. Upon concentration in vacuo, the crude extracts were tested against a variety of Gram-positive and Gram-negative strains of bacteria using the agar disk diffusion method. Antimicrobial activity was demonstrated against level 2 Staphylococcus aureus and seen in roots and stems of all species except R. aureum. The methanol extracts were further partitioned by solubility in three solvents (water, ethyl ether and methylene chloride) to test antimicrobial activity on S. aureus. The methanol- and water-soluble extracts of R. bracteosum and R. sanguineum exhibit the highest degree of antimicrobial activity, thus chromatographic studies (e.g. GC-MS) will focus on these extracts in order to progress toward the identification of the biologically active components.