Capstone Talks 2009

2009 Capstone Celebration Symposium

PLU Chemistry Department

April 27th to May 1st, 2009

Come and join the chemistry department to hear the senior capstone presentations. Student presentation swill occur Monday through Friday. The schedule of talks with more details is given below.

[ Monday | Tuesday | Wednesday | Thursday | Friday ]

All talks will be held in the Morken Center in Room 103!

12:40 pm - Using NMR to Determine the pKa of Histidine in Piscidin 1, an Antimicrobial Peptide

Elaina Bonar, Senior Capstone Seminar

Piscidin is an antimicrobial, cationic, amphipathic peptide that is 22 amino acids in length and adopts an α-helical shape. In this investigation, the pKa of histidine at position 17 is investigated in the presence of DMPC and DMPG lipids and SDS micelles using solid state NMR with Magic Angle Spinning (MAS) and solution NMR, respectively. It was determined that the pKa was around 6.0-6.8 and can be correlated with the efficiency of lipid perturbation. The data from this and other structure-function relationship studies can be applied towards the development of novel antibiotics to be used against multi-resistant antibiotics.

1:50 pm - Anionic Synthesis of Multi-Block Copolymers Under Inert Conditions

Kurtis Fairley, Senior Capstone Seminar

Multiblock copolymers are thought to be very effective additives in polymer blends. Multiblock copolymers of polybutadiene and polystyrene were synthesized using positive pressure anionic techniques. These particular multiblock copolymers will be useful to compare with data from other previously studied polymer blend systems with related additives. Basic diblocks and a triblock were initially synthesized. Additionally, a series of tetrablocks were synthesized consisting of four equal segment molecular weights of polystyrene and polybutadiene. All of the polymers were synthesized under inert conditions in cyclohexane with a positive pressure of argon. The multiblock copolymers were characterized by NMR and GPC and resulted in narrow polydispersity with the desired compositions. These copolymers are now under investigation for their compatibilization effects on the phase behavior of a polybutadiene/polystyrene blend.

1:50 pm - Phase Boundary Behavior of a Polymer Blend Modified by Addition of Diblocks Varying in Composition and Concentration Added

Michael Barich, Senior Capstone Seminar

Phase behavior of a polystyrene (PS), polybutadiene (PB), and diblock blends were evaluated using cloud point analysis. Seven different diblock copolymers were used with varying PS/PB percent composition. The diblocks were introduced at 5% and 10% by mass amounts into five different PS/PB percent by mass solutions (25, 33, 39, 50 and 60% PB). The results showed that a shift in the critical temperature was present, both shifting the PS/PB composition of the blend as well as the temperature. With more extreme diblock compositions, a greater raise in the critical temperature and a larger shift in critical composition away from previous research. Comparisons to predictions of Dudowicz, et al. are discussed.

2:30 pm - Aziridinomitosene as a DNA Interstrand Cross-linking Agent

Christina Tieu, Senior Capstone Seminar

Many chemotherapy agents are bis-alkylating compounds which are capable of forming covalent bonds to both strands of double stranded DNA. The formation of this cross-link prevents cell replication and may lead to cell death. Various classes of compounds may act as bis-alkylating agents; previously studied classes include nitrogen mustards and mitomycins. Current studies are focused on aziridinomitosene, which is structurally similar to mitomycin C. Aziridinomitosene contains both a quinone moiety and an aziridinium ring; both functional groups are necessary in the mechanism of cross-link formation. Incubating aziridinomitosene with duplex DNA has yielded monoadduct and cross-linked products which may be identified after separation with DPAGE. Follow-up experiments have shown that the binding of aziridinomitosene is sequence specific (CG dinucleotides are favored). It was also shown that covalent bonds form between C1 and an amino group on C2 of guanine as well as C10 and an amino group on another guanine base to form the cross-link. Further research is ongoing to elucidate to better understand the compounds viability as a chemotherapy agent.

3:20 pm - Antimicrobial Properties of Bark and Root Extracts from Native Ribes species

Daniel Hibbard, Senior Capstone Seminar

Solid state Nuclear Magnetic Resonance (ssNMR) was used to determine the structure of piscidin, a 22 residue amphipathic antimicrobial peptide isolated from hybrid striped bass. Peptide samples were oriented in biologically-mimicking lipid membrane mixtures. 15N and 1 H chemical shifts and 15N-1H dipolar couplings collected on high magnetic field instruments were processed for high resolution structural determination. Additional work was accomplished toward creating a recombinant peptide from and E. coli strain that could ultimately be uniformly 15N-labeled. A 10-site 15N-backbone labeled peptide, by far the most labeled peptide on this project to date, was studied by ssNMR to start establishing a strategy to handle data from a uniformly-labeled lipid-bound piscidin.

4:00 pm - Solid-state NMR Studies of α-Helical Piscidin-1 and KL11 β−sheet Antimicrobial Peptides

Eric Gordon, Senior Capstone Seminar

Piscidin is an antimicrobial cationic amphipathic peptide isolated from hybrid striped bass and exists in multiple forms. Structural, dynamic, and topological studies are all run on the peptide in order to help elucidate its mechanism of action. Of the studies, two aspects will be focused on in the presentation. One is the elucidation of the full 15N backbone structure of piscidin 1. The other is the effect of raised pH over that of near physiological pH. Hydrated oriented samples were prepared and solid state nuclear magnetic resonance experiments were run on them in order to obtain the information. In collaboration efforts, the β-sheet W2KL11 peptide was subjected to structural and topological studies as well.

1:50 pm - Teaching through Experiments: Laboratory Experiments in the High School Chemistry Curriculum

Marie Reardon, Senior Capstone Seminar

Teaching science is a unique experience. Not only is there an expectation that a set of concepts that must be taught, but it is also necessary to provide students with authentic hands-on demonstrations and experiments. Thus, the development of a yearlong, safe, “green” chemistry laboratory curriculum that addresses the needs and physical limitations of public schools is essential for future chemistry educators.

2:30 pm - Dissolution of Suspended Sediments from the Nisqually Glacier

Luke Weinbrecht, Senior Capstone Seminar

The dissolution kinetics of sediments taken from the Nisqually River was measured under field like conditions to investigate the chemical weathering present in the alpine environment. An evaluation of prewash methods was performed to determine the influence this may have on the dissolution of selected sediments. Initial rates were used to compare the differences as well as the use of a SEM for imaging and an EDX for chemical composition. It was determined that prewash methods do affect the overall concentration change, but do not significantly change the initial rates of dissolution. Using the EDX data we were able to determine that there was change occurring on the sediment surfaces during the prewash as well as during sediment dissolution. This data can be used in the field to better understand river composition and the implications this may have on global climate change .

3:15 pm - Synthetic study of 2,2’-carbonyldiisoxazoldine: A Novel Route to Unsymmetric Ketones

Mycah Uehling, Senior Capstone Seminar

Unsymmetric ketones as 6π electrocyclization substrates have come into a new phase of synthesis with the investigation of 2,2′-carbonyldiisoxazolidine (isoxazolidine urea). Multiple routes to isoxazolidine urea were studied. In general there are two ways to make derivatized ureas. 1) Make the ureas first, then substitute the urea or 2) substitute the nitrogen nucleophile first then react it with a carbonic acid derivative. Optimization of one synthesis of isoxazolidine urea was completed. The limiting factors that were  discovered to cause low yielding reactions of the optimized route were purity of reagents and the hygroscopicity of a key intermediate salt (isoxazolidine hydrochloride). While optimizing the synthesis of isoxazolidine urea a larger synthetic puzzle was encountered. A convenient, high-yielding general route to N,N’-dihydroxyurea and its derivatives is lacking in the literature. Different routes to access isoxazolidine urea were explored with emphasis on N,N’-dihydroxyurea and relevant key intermediates. A previously-optimized pathway involving the addition of 2 mol equiv. isoxazolidine hydrochloride to the water-reactive carbonic acid derivative 1,1′-carbonyldiimidazole (78% yield) is still the best yielding route to date.

4:00 pm - Developments Towards a Catalytic Wittig Olefination Reaction Using Triphenylarsine

Quang-Loc Hua, Senior Capstone Seminar

Triphenylarsine was used under different reaction conditions in order to determine favorable conditions for its use in a catalytic Wittig olefination reaction. A screen of reaction variables includes pH, order of addition of reactants, reducing agent, temperature, and reaction time revealed new insights into the complex reactions mixture. The reactions were monitored using a gas chromatography/mass spectrometry and thin layer chromatography.

1:50 pm - Atomic force microscopy of high molecular weight thin film polymer blends compatibilized with triblock and graft copolymers

E. Moriah Zimmerman, Senior Capstone Seminar

Thin film polymer blends were studied using atomic force microscopy (AFM) with focus on the effect that various triblock and multi-arm graft copolymers have on the surface morphology. Polystyrene and polybutadiene homopolymer blends at critical volume and above their entanglement molecular weights were studied with added copolymer up to 11% (w/w). Two triblock copolymers of different segment molecular weights and three graft copolymers with varying number of arms were used as additives. The samples were spin-coated onto cover slips at a 65 nm thickness. The blend surfaces were analyzed using an Asylum MFP-3D AMF in AC mode. Surface roughness as well as for lateral domain size using Fourier transform techniques were studied for the as-spun thin films. The added copolymers had a minimal influence on the surface morphology. Anneal-quench data was also studied for the blend films with 9% (w/w) added copolymer.

2:30 pm - The Preparation of Disubstituted Ureas By Carbonylation of S,S-Dimethyldithiocarbonate with Primary and Secondary Amines

Hunter Simpson, Senior Capstone Seminar

A method is proposed to use dimethyl dithiocarbonate (DMDTC) to prepare symmetrical hydroxyureas. DMDTC is advantageous to phosgene because it is less toxic, gives off non-toxic byproducts, and the product can be very easily isolated. This procedure was tested for primary and secondary amines, and showed that it was only possible for primary amines to react with DMDTC. Secondary amines did not react with DMDTC under a variety of varied conditions, and showed that steric hindrance would not allow a reaction to occur under mild conditions. Reactions were performed using water and methanol as solvents in varying concentrations. N,N’-Dihydroxyurea was prepared at 55C with a molar ratio DMDTC:hydroxylamine of 1:4. The products of these reactions were analyzed using IR spectroscopy, NMR spectroscopy and gas chromatography/mass spectrometry.

3:20 pm - Examining Polymer Surface Properties Using AFM Force Curve Measurements

Alicia Che, Senior Capstone Seminar

AC mode imaging, static and dynamic force curve measurements using an atomic force microscopy were carried out on physical properties and characteristics of polystyrene (PS), polybutadiene (PB) and PS/PB blend film using an atomic force microscopy (AFM).  AC imaging, static and dynamic force curve measurements were carried out on the samples. While static force curves revealed important physical properties of both PS and PB, dynamic force curves were found to be more effective in characterizing the different domains in the polymer blend.

4:00 pm - Characterization of Hydrogen/Deuterium Exchange in the Amphipathic Helices of Piscidin 1

Anna Kozlova, Senior Capstone Seminar

It has been established by previous studies that membrane-bound piscidin 1 adopts an  structure. Under such an arrangement hydrophilic residues would be exposed to the aqueous environment, while hydrophobic residues would be interacting with the cell membrane. In an oriented sample, while mimicking natural environment and physiological condition and exposing residues to deuterium oxide, observation was made possible of exchange that took place. More specifically, high-resolution solid-state NMR spectra were obtained from hydrogen/deuterium exchange that took place in the isotopically backbone-labeled piscidin 1 oriented in the lipid layer.

1:10 pm - A Biochemical Review of Serotonin: An Essential Neurotransmitter

Alecia Chang, Senior Capstone Seminar

Serotonin or 5-hydroxytryptamine (5-HT) is a well studied monoamine neurotransmitter first observed in the 1930s as a serum factor. It is synthesized in a two step process using the precursor L-tryptophan. The first and rate determining step is catalyzed by tryptophan hydroxylase (TPH) and then further modified by aromatic amino acid decarboxylase (AAADC). Under the control of a feedback regulation system, 5-HT levels in both intra- and extracellular are carefully maintained. The serotonergic system is essential for both central nervous system (CNS) and periphery. Interactions with various receptors gives 5-HT different functions. Due to its diverse affects on bodily functions and high selectivity for receptors, it is a target for many different types of medications for various disorders. Because of this, a lot of current research is underway to better understand this very important system through genetic and pharmacological studies. Deeper and further understanding of 5-HT receptors can help create or modify current medications to have higher efficiency and lower side effects.

1:50 pm - Antimicrobial Properties of Bark and Stem Extracts from Ribes Species Native to the Pacific Northwest

Cenafer Carino, Senior Capstone Seminar

Two species from the Ribes genus native to the Pacific Northwest were targeted to extract and characterize antimicrobial compounds. The stems and bark of R. Sanguineum and R. Lacustre were cut into pieces and blended before being air-dried. Air-dried bark and stems of each plant were refluxed with petroleum ether and then methanol. Crude extracts were obtained after rotary evaporation and high vacuum concentration of the methanol extracts. Thin layer and flash column chromatographic techniques were applied to find biologically active compounds, and antimicrobial activities of each species were measured using the disk diffusion method on Mueller Hinton agar. Activity was based on the zones of inhibition created on Gram-positive and Gram-negative strains of Staphylococcus aureus and Escherichia coli, respectively, from a serial dilution of each plant extract in methanol. The extracts from R. Sanguineum showed the most activity with measurable zones of inhibition against S. aureus.