SMARTech Collection: Undergraduate Research Option Theses

Amino Acid Profiling by Reactive Desorption Electrospray Ionization Tandem Mass Spectrometry (DESI-MS/MS)

Sat, 28 Nov 2009 22:58:59 GMT

Title: Amino Acid Profiling by Reactive Desorption Electrospray Ionization Tandem Mass Spectrometry (DESI-MS/MS)

Authors: Rizzo, David G.

Abstract: Desorption electrospray ionization mass spectrometry (DESI MS) has gained significant recognition over the past few years because of its simplicity and rapid throughput capabilities, allowing for the direct analysis of samples with a wide variety of sizes, shapes, and chemistries. Addition of various reagents into the DESI spray solvent enables atmospheric pressure ion molecule reactions between these reagents in the charged micro droplets and analyte molecules on the sample surface affording improved selectivity and sensitivity in some cases. Presented is a rapid screening method for amino acids (aas) based on reactive DESI. Amino acids have been shown to play key roles in the regulation of cellular processes. They are also particularly vital in the determination of metabolic disorders such as phenylketonurea, homocystinuria, and tyrosinemia. The most specific and reliable methods for diagnosing these disorders are based on the determination of aas in body fluids using methodologies such as gas/liquid chromatography, tandem MS, and various combinations thereof. However, these methods are usually time-consuming, increasing the time physicians wait before administering treatment or regulating the diet of diseased infants. The reactive DESI approach presented here is based on the formation of stable noncovalent complexes between alpha-cyclodextrin (dissolved in the spray solvent) and amino acids present in the sample affording a selective method for their detection. However, the selectivity and sensitivity of screening for aas was improved by performing the MS analysis in the multiple reaction monitoring mode when using a quadrupole ion trap or by the precursor ion scan when using a triple quadrupole MS instrument, affording an average twenty-five times sensitivity improvement compared to analysis in full scan mode. The observation of similar complexes with various carboxylic acids including formic acid and acetic acid, and evidence from tandem MS experiments indicate that amino acid:alpha-cyclodextrin complexation reactions occur by hydrogen bonding interaction with carboxyl group of the aas. The specificity and sensitivity provided by this approach seems very promising for applications in the rapid screening of aas directly from body fluids including urine and plasma for amino acid disorders in a clinical setting.

Zinc Oxide coated Carbon Nanotubes as Piezoelectric Nanogenerators

Sat, 28 Nov 2009 22:58:59 GMT

Title: Zinc Oxide coated Carbon Nanotubes as Piezoelectric Nanogenerators

Authors: Mason, Celeste

Abstract: Piezoelectric nanogenerators were created using two designs: coating carbon nanotubes (CNTs) grown on a silicon wafer substrate with a thin film of zinc oxide (ZnO), coupled with an additional gold-coated CNT grown wafer to act as an electrodes and coating carbon nanotubes (CNTs) grown on carbon fiber with each type of coating to form flexible electrodes. The CNTs on all samples were grown using a standard recipe, with thermally evaporated iron as catalyst. ZnO deposition techniques such as RF sputtering and ion-assisted deposition were used. Gold deposition was accomplished by thermal evaporation and RF sputtering. Once electrodes were combined, preliminary electrical testing resulted in measurement of current densities of up to 4.2x10-7 A/cm3. Additional electrical measurements indicated that the current generated was the result of piezoelectric behavior of the ZnO coating. These values may be increased with better penetration of both gold and ZnO coatings during deposition on the CNTs. Improvement of film quality, such as gold adhesion and ZnO crystal orientation, may also increase current generation.

Nanoparticle-mediated r-depression in the rotifer Brachionus manjavacas

Sat, 28 Nov 2009 22:58:59 GMT

Title: Nanoparticle-mediated r-depression in the rotifer Brachionus manjavacas

Authors: Hicks, Daniel

Abstract: Nanotechnology research promises novel and practical applications of well-characterized materials. However, responsible development of the nanotechnology industry necessitates proactive research into the ecological responses of communities to the presence of nano-scale materials. I attempt to discern if and how the presence of inert nanoparticles at varying concentrations and size affects the fitness of populations of Brachionus manjavacas (Rotifera). Feeding fluorescently labeled 50 nm latex microspheres to rotifers produced dramatic fluorescence distributed throughout the females and their eggs. Fluorescent intensity was distinct from background epifluorescence exhibited by B. manjavacas, and increased with concentration, availability of food, and duration of exposure. Transfer of exposed maternal females and F1 offspring into nanoparticle-free environments demonstrated that these nanoparticles were rapidly cleared from the animals, and that the offspring suffered no significant effects from parental exposure. However, the population growth rate was depressed 50% in rotifer cultures exposed to 0.30 ug/mL of 50 nm particles, and 89% in cultures with nanoparticle concentrations of 1.14 ìg/mL. Nanoparticles of identical composition but of larger diameter (up to 3000 nm, comparable to algae cells, a natural food source), caused no reduction in population growth rate. These larger particles remained confined in the gut, implicating nanoparticle size as a critical factor in bioactivity. Causes of growth rate depression include, but are not limited to, a marked decrease in feeding behavior. Mode of entry is suspected to be either epithelial digestive-tract phagocytosis or introduction through cellular pores.

Training Novices on Hierarchical Task Analysis

Sat, 28 Nov 2009 22:58:59 GMT

Title: Training Novices on Hierarchical Task Analysis

Authors: Felipe, Sarah

Abstract: The training of a complex task such as task analysis is an area that very few have explored. This study examines how different training methods affect knowledge acquisition, focusing on content learned and errors made by novices in the initial phase of learning of Hierarchical Task Analysis (HTA). Three types of declarative instructions were compared: procedures, decision/actions, and concept map, which were representative of different types of diagrams (matrix, network, hierarchy). Participants were assigned to one of the training conditions and instructed to perform task analyses of five different tasks (making a piece of toast, making a cup of coffee, painting a door, making a phone call, and making Vetkoek - a South African main course). Questionnaire data (declarative knowledge) and task analyses (procedural knowledge) were coded on five criteria: hierarchical representation, stating high-level goal, stating plan, stating subgoals, and satisfaction criteria. Results indicated that participants identified some criteria (goals, subgoals) more often than others as being representative of HTA (hierarchical representation). Furthermore, the nature of the task had a greater effect on the knowledge acquired about HTA than the differences in training material at this early stage of learning. During initial training of HTA it is important that more detailed instruction materials be distributed to allow for greater understanding of HTA. This study informs research about various types of diagrams and also adds to the literature on training HTA.