Browsing by Author "Van Orden, Alan K., committee member"
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Item Open Access Development of methods for assessing oxidative stress caused by atmospheric aerosols(Colorado State University. Libraries, 2012) Sameenoi, Yupaporn, author; Henry, Charles S., advisor; Rovis, Tomislav, committee member; Farmer, Delphine K., committee member; Van Orden, Alan K., committee member; Kipper, Matthew J., committee memberExtensive epidemiological studies show strong associations between the exposure to atmospheric aerosol particulate matter (PM) in the size range of 0.1- 10 µm and health problems, including respiratory, atherosclerosis and cardiovascular diseases. However, the mechanisms of PM-induced toxicity are poorly understood. A leading hypothesis states that airborne PM induces harm by generating reactive oxygen species in and around human tissues, leading to oxidative stress. To improve understanding of this effect, methods including biological assays and chemical assays for assessing oxidative stress caused by atmospheric aerosols have been developed and are described in this dissertation. For biological assays, a cleavable tag immunoassay (CTI) was developed with an ultimate goal of measuring multiple oxidative stress biomarkers in a single run. As a proof-of-concept, the multianalyte analysis system CTI was performed in competitive, non-competitive, and mixed formats for detection of small molecules and protein biomarkers simultaneously. For chemical assays, a microfluidic electrochemical sensor and a microfluidic paper-based analytical device (µPAD) have been developed for assessing aerosol oxidative stress in an area-based exposure study and a personal exposure study, respectively. The microfluidic electrochemical sensor was used for assessing aerosol oxidative stress by measuring the oxidative activity. The sensor was coupled directly to a Particle-into-Liquid-Sampler (PILS) to create an on-line aerosol sampling/analysis system. The system offers analysis with 3 minute temporal resolution, making it the best available temporal resolution for aerosol oxidative activity. The sensor was also used to analyze the ability of aerosols to generate hydroxyl radicals as another parameter for assessing aerosol oxidative stress. The ultimate goal of this system is to create an on-line monitoring system using a similar approach for oxidative activity analysis. As a first step toward this goal, assay optimization and system characterization in an off-line format employing flow injection analysis and amperometric detection, were carried out and presented in this dissertation. A microfluidic paper-based analytical device (µPAD) was developed for measuring oxidative activity of aerosol collected by a personal sampler. The system allows analysis with minimal sample preparation and requires 100-fold less particulate matter mass than existing analysis methods.Item Open Access Femtosecond to nanosecond transient absorption studies of aqueous solvation and deprotonation dynamics in confinement(Colorado State University. Libraries, 2011) Cole, Richard Leo, author; Levinger, Nancy E., advisor; Bernstein, E. R. (Elliot R.), committee member; Ladanyi, Branka M., committee member; Van Orden, Alan K., committee member; Bartels, Randy, committee memberWe explore the use of logarithmic based optical delay in time-resolved data collection. We show that logarithmic spacing of data points provides an economical way to collect data over many decades of time which speeds data collection. We present a simple algorithm to generate time delay points for application in time-resolved data collection. We test the use of logarithmic vs. linear data collection over six orders of magnitude by measuring broadband femtosecond transient absorption (BFTA) spectra of HPTS in pH-7 water from femtoseconds to nanoseconds. Statistical analysis of logarithmic and linear data collection show that linear data collection shows a clear advantage by requiring a fewer number of time-delay points to achieve a given precision in subsequent data analysis. We investigate solvation dynamics (SD) via coumarin 343 (C343) in Aerosol OT (sodium bis(2-ethylhexyl) sulfosuccinate, AOT) reverse micelles with varying water content through broadband femtosecond transient absorption experiments. These studies build upon our previous studies of SD in the AOT reverse micelles through time-resolved fluorescence Stokes shift (TRFSS) experiments (J. Phys. Chem. B, 1998, 102, 2705) which limited data collection to approximately 100 ps. We extend the experimental time window to 2 nanoseconds and recover the entire solvation response. These results combined with steady-state spectra and reorientation dynamics indicate that C343 exists in two distinct populations within the reverse micelles which correlate with interfacial and core water. Our results suggest that translational motion of C343 may contribute to the total observed solvation response. We study excited state proton transfer (ESPT) of HPTS (8-hydroxypyrene-1,3,6-trisulfonic acid trisodium salt) in cationic (cetyltrimethylammonium bromide, CTAB), anionic (AOT), and nonionic (polyoxyethylene (5) isooctylphenyl ether, IGE) reverse micelles by BFTA. For larger AOT RM, ESPT dynamics are found to be approximately equal to the dynamics found in bulk water. As the size of the AOT RM approaches the size of the probe molecule, ESPT becomes increasingly quenched. For all sizes of CTAB RM, HPTS ESPT is found to be 10-20 times slower than HPTS ESPT in bulk water. This result combined with reorientation measurements suggest that HPTS resides at the interfacial region in CTAB RM and thus remains immobilized. In IGE RM, ESPT is 4-10 times slower than bulk water behavior which we contribute to immobilization of HPTS in the micelle interface. HPTS reorientational motion is hindered with respect to bulk HPTS motion. We measure the kinetic isotope effect (KIE) on HPTS ESPT dynamics and results suggest that the solvent plays a significant role in the observed dynamics only in the largest IGE reverse micelles. Steady-state absorption measurements show that HPTS exists in a unique environment within IGE RM which contrasts with HPTS in other nonionic reverse micelle systems.Item Open Access Fundamental investigations of hydrocarbon plasma chemistry: mechanistic studies of gas-phase processes and plasma-surface interactions(Colorado State University. Libraries, 2020) Van Surksum, Tara, author; Fisher, Ellen R., advisor; Van Orden, Alan K., committee member; Ravishankara, A. R., committee member; Weinberger, Christopher R., committee memberTo view the abstract, please see the full text of the document.Item Open Access Interactions of biologically active molecules, cofactors, and drugs with model membranes(Colorado State University. Libraries, 2021) Van Cleave, Cameron, author; Crans, Debbie C., advisor; Van Orden, Alan K., committee member; Levinger, Nancy E., committee member; Roess, Deborah A., committee memberThe cell membrane is important for the structure, function, and overall homeostasis of the cell. It consists mainly of phospholipids which have different physicochemical and material properties. As such, molecular interactions between the membrane's components and its environment are of importance. This manuscript explores the interactions of different classes of molecules with model membrane systems to gain a fundamental understanding. Chapter 1 provides background on the cell membrane and current models as well as an introduction to lipoquinones and small molecule drugs. Chapter 2 discusses the interactions of menadione and menadiol with Langmuir monolayers and reverse micelles. Menadiol and menadione are representative of the headgroup of menaquinones, a class of electron transporter, hence they are redox active. We hypothesized that the respective locations of menadione and menadiol within the membrane would vary due to their different physicochemical properties. We used Langmuir monolayers and NMR of reverse micelles to explore the location and association of menadione and menadiol with model membrane interfaces. Chapter 3 investigates the location, association, and conformation of truncated menaquinones with Langmuir monolayers and simulated bilayers. Previous work found that truncated menaquinones fold at the interface of a reverse micelle, so we hypothesized that subtle differences in folding would cause variations in location and association with phospholipids. We used a combination of Langmuir monolayers and molecular dynamics simulations to probe location, association, and conformation of truncated menaquinone homologues, MK-1 through MK-4, in a phospholipid membrane. Chapter 4 explores the pH-dependent effects of two anti-tubercule molecules at the membrane interface. Recent studies have suggested that pyrazinoic acid behaves as a protonophore and we further explored this suggestion while simultaneously exploring physicochemical properties of pyrazinoic acid and pyrazinamide. This chapter utilized a combination of Langmuir monolayers, NMR, and fluorescence leakage studies to characterize the molecular interactions of pyrazinoic acid with model membranes so that POA could be compared to a previous study with benzoic acid, a known protonophore.Item Open Access Low temperature solution synthesis of ZnSb, MnSb, and Sr-Ru-O compounds(Colorado State University. Libraries, 2011) Noblitt, Jennifer Lenkner, author; Prieto, Amy L., advisor; Dandy, David S., committee member; Elliot, C. Michael, committee member; Fisher, Ellen R., committee member; Van Orden, Alan K., committee memberIncreasing energy demands are fueling research in the area of renewable energy and energy storage. In particular, Li-ion batteries and superconducting wires are attractive choices for energy storage. Improving safety, simplifying manufacturing processes, and advancing technology to increase energy storage capacity is necessary to compete with current marketed energy storage devices. These advancements are accomplished through the study of new materials and new morphologies. Increasing dependence on and rising demand for portable electronic devices has continued to drive research in the area of Li-ion batteries. In order to compete with existing batteries and be applicable to future energy needs such as powering hybrid vehicles, the drawbacks of Li-ion batteries must be addressed including (i) low power density, (ii) safety, and (iii) high manufacturing costs. These drawbacks can be addressed through new materials and morphologies for the anode, cathode, and electrolyte. New intermetallic anode materials such as ZnSb, MnSb, and Mn2Sb are attractive candidates to replace graphite, the current industry standard anode material, because they are safer while maintaining comparable theoretical capacity. Electrodeposition is an inexpensive method that could be used for the synthesis of these electrode materials. Direct electrodeposition allows for excellent electrical contact to the current collector without the use of a binder. To successfully electrodeposit zinc and manganese antimonides, metal precursors with excellent solubility in water were needed. To promote solubility, particularly for the antimony precursor, coordinating ligands were added to the deposition bath solutions. This work shows that the choice of coordinating ligand and metal-ligand speciation can alter both the electrochemistry and the film composition. This work focuses on the search for appropriate coordinating ligands, solution pH, and bath temperatures so that high quality films of ZnSb, MnSb, and Mn2Sb may be electrochemically deposited on a conducting substrate. Increasing use of natural resources for energy generation has driven research in the area of energy storage using superconducting materials. To meet energy storage needs the materials must have the following features: (i) safety, (ii) superconductivity at or above liquid nitrogen temperature (77 K), (iii) low cost manufacturing processes, and (iv) robustness. The search for materials that meet all of these criteria is on-going, specifically in the area of high temperature superconductivity. The precise mechanism of superconductivity is not known. A few theories explain some of the phenomenological aspects, but not all. In order to logically select and synthesize high temperature superconductors for industrial applications, the precise mechanism must first be elucidated. Additionally, a synthetic method that yields pure, high quality crystals is required because transition temperatures have been shown to vary depending on the preparation method due to impurities. Before measuring properties of superconductors, the development of a synthesis method that yields pure, high quality crystals is required. Most superconductors are synthesized using traditional solid state methods. This synthesis route precludes formation of kinetically stable phases. Low temperature synthesis is useful for probing thermodynamic verses kinetic stability of compounds as well as producing high quality single crystals. A novel low temperature hydrothermal synthesis of Sr-Ru-O compounds has been developed. These materials are important because of their interesting properties including superconductivity and ferromagnetism. Sr2RuO4 is particularly interesting as it is superconducting and isostructural to La2CuO4, which is only superconducting when doped. Therefore, Sr2RuO4 is a good choice for study of the mechanism of superconductivity. Additionally, new kinetically stable phases of the Sr-Ru-O family may be formed which may also be superconducting. Sr-Ru-O compounds were previously synthesized via the float zone method. There is one report of using hydrothermal synthesis, but the temperatures used were 480-630 °C. In general, hydrothermal methods are advantageous because of the potential for moderate temperatures and pressures to be used. Additionally, the reaction temperature, precursor choice, and reaction time can all be used to tune the composition and morphology of the product. Hydrothermal methods are inexpensive and a one-step synthesis which is very convenient to scale up for industrial application. This work shows how a hydrothermal method at temperatures between 140 °C and 210 °C was developed for the synthesis of the Sr-Ru-O family of compounds.Item Open Access Microchip capillary electrophoresis: improvements using detection geometry, on-line preconcentration and surface modification(Colorado State University. Libraries, 2012) Guan, Qian, author; Henry, Charles S., advisor; Strauss, Steven H., committee member; Van Orden, Alan K., committee member; Krummel, Amber, committee member; Hanneman, William H., committee memberCapillary electrophoresis and related microfluidic technologies have been utilized with great success for a variety of bioanalytical applications. Microchip capillary electrophoresis (MCE) has the advantages of decreased analysis time, integrated sample processing, high portability, high throughput, minimal reagent consumption, and low analysis cost. This thesis will focus on the optimization of our previous microchip capillary electrophoresis coupled electrochemical detection (MCE-ECD) design for improved separation and detection performance using detection geometry, on-line preconcentration and surface modification. The first effort to improve detection sensitivity and limits of detection (LODs) of our previous MCE-ECD system is established by an implementation of a capillary expansion (bubble cell) at the detection zone. Bubble cell widths were varied from 1× to 10× the separation channel width (50 μm) to investigate the effects of electrode surface area on detection sensitivity, LOD, and separation efficiency. Improved detection sensitivity and decreased LODs were obtained with increased bubble cell width, and LODs of dopamine and catechol detected in a 5× bubble cell were 25 nM and 50 nM respectively. In addition, fluorescent imaging results demonstrate ~8% to ~12% loss in separation efficiency in 4× and 5× bubble cell, respectively. Another effort for enhancing detection sensitivity and reducing LODs involves using field amplified sample injection and field amplified sample stacking. Stacking effects were shown for both methods using DC amperometric and pulsed amperometric detections. Decreased LODs of dopamine were achieved using both on-line sample preconcentration methods. The use of mixed surfactants to affect electroosmotic flow (EOF) and alter separation selectivity for electrophoretic separations in poly(dimethylsiloxane) (PDMS) is also presented in this thesis. First the effect of surfactant concentration on EOF was studied using the current monitoring method for a single anionic surfactant (sodium dodecyl sulfate, SDS), a single zwitterionic surfactant (N-tetradecylammonium-N,N-dimethyl-3-ammonio-1-propane sulfonate, TDAPS), and a mixed ionic/zwitterionic surfactant system (SDS/TDAPS). SDS increases the EOF as reported previously while TDAPS shows an initial increase in EOF followed by a reduction in EOF at higher concentrations. The addition of TDAPS to a solution containing SDS makes the EOF decrease in a concentration dependent manner. The mixed SDS/TDAPS surfactant system allows tuning of the EOF across a range of pH and concentration conditions. After establishing EOF behavior, the adsorption/desorption rates were measured and show a slower adsorption/desorption rate for TDAPS than SDS. Next, capacitively coupled contactless conductivity detection (C4D) is introduced for EOF measurements on PDMS microchips as an alternative to the current monitoring method to improve measurement reproducibility. EOF measurements as a function of the surfactant concentration were performed simultaneously using both methods for three nonionic surfactants, (polyoxyethylene (20) sorbitan monolaurate (Tween 20), polyoxyethylene octyl phenyl ether (Triton X-100), polyethylene glycol, (PEG 400)), mixed ionic/nonionic surfactant systems (SDS/Tween 20, SDS/Triton X-100, and SDS/PEG 400) and mixed zwitterionic/nonionic surfactant systems (TDAPS/Tween 20, TDAPS/Triton X-100, and TDAPS/PEG 400). EOF for the nonionic surfactants decreases with increasing surfactant concentration. The addition of SDS or TDAPS to a nonionic surfactant increases EOF relative to the pure nonionic surfactant. Next, separation and electrochemical detection of two groups of model analytes were explored using mixed surfactant systems. Similar analyte resolution with greater peak heights was achieved with mixed surfactant systems relative to the single surfactant system. Finally, the utility of mixed surfactant systems to achieve improved separation chemistry of biologically relevant compounds in complex sample matrixes was demonstrated in two applications, which include the detection of catecholamine release from rat pheochromocytoma (PC12) cells by stimulation with 80 mM K+ and the detection of reduced glutathione (GSH) in red blood cells (RBCs) exposed to fly ash suspension as a model environmental oxidant.Item Open Access Part 1, executed electronic state decomposition of energetic molecules. Part 2, conformation specific reactivity of radical cation intermediates of bioactive molecules(Colorado State University. Libraries, 2010) Bhattacharya, Atanu, author; Bernstein, Elliot R., advisor; Levinger, Nancy E., committee member; Van Orden, Alan K., committee member; Szamel, Grzegorz, committee member; Bartels, Randy A., committee memberEnergetic materials have a wide variety of industrial, civil, and military applications. They include a number of organic compounds such as RDX (1,3,5- trinitroheahydro-s-triazine), HMX (octahydro-1,3,5,7-tetranitro-l ,3,5,7-tetrazocine), DAAF (3,3'-diamino-4,4'-azoxyfurazan), DAATO35 (3,3'-azobis(6-amino-l,2,4,5- tetrazine)-mixed N-oxides), etc. These materials release huge chemical energy during their decomposition. The decomposition of energetic materials is initiated with a shock or compression wave or a spark. Such events in solids generate molecules in the excited electronic states. Hence, in order to maximize release of the stored chemical energy in the most efficient and useful manner and to design new energetic materials, the unimolecular decomposition mechanisms and dynamics from excited electronic states should be understood for these systems. This thesis describes understanding about unimolecular decomposition of energetic materials from their excited electronic states. A few fundamental questions at molecular level dealing with electronic excitation of energetic materials are addressed here: (a) what happens immediately after electronic excitation of energetic molecules?; (b) how is excess energy partitioned among product molecules following electronic excitation?; (b) what are the mechanism and dynamics of molecular decomposition?; (d) does nonadiabatic chemistry (a process that span multiple electronic potential energy surfaces) through conical intersection (crossing of different potential energy surfaces) dominate system behavior? Both energy and time resolved spectroscopic techniques are used in this effort. The product internal state (rotational and vibrational) distributions are probed using mass and energy resolved spectroscopic techniques using time-of-flight mass spectrometry (TOFMS) and laser induced fluorescence (LIF) spectroscopy. Analyzing the product internal state distributions, the mechanisms of unimolecular decomposition of energetic molecules from excited electronic states are determined. The femtosecond pump-probe spectroscopic technique is utilized to determine ultrafast decomposition dynamics of these molecules. From a theoretical point of view, multiconfigurational methodologies such as, CASSCF and CASMP2 are used to model the processes involving excited electronic states of energetic molecules. Influence of nonadiabatic chemistry in the overall decomposition of energetic molecules is also theoretically judged. The primary energetic systems whose nonadiabatic chemistry discussed here are the nitramine (e.g., RDX, HMX), furazan (e.g., DAAF), and tetrazine-N-oxide (e.g., DAATO3.5) based energetic species. A number of model systems, which are simple analogue molecules of the large and more complex energetic materials, are studied in detail to understand nonadiabatic energetic behavior of a single energetic moiety of particular class. Subsequently, the decomposition mechanism for more complex energetic systems are studied and compared with that of their model systems. Nitramine energetic materials and model systems undergo nitro-nitrite isomerization followed by IV NO elimination. Nitramine energetic materials dissociates in the ground state generating rotationally cold (20 K) distribution of the NO product. Nitramine model systems dissociates in the excited state surface producing rotationally hot (-120 K) distribution of the NO product. The nitro-nitrite isomerization happens through conical intersection. Furazan based model molecules (e.g., furazan) possess two different pathways of decomposition: ring contraction and ring opening. These two pathways are electronically nonadiabatic. The ring contraction mechanism generates rotationally cold (20 K) product NO and the ring opening mechanism generates rotationally hot (100 K) product NO. Furazan based energetic material (DAAF), however, dissociates only through a ring contraction mechanism. Thus nonadiabatic pathways control the decomposition of furazan based molecules. Decomposition of tetrazine-2,4-dioxide based molecules involves a ring contraction mechanism through (Si/So)ci, producing only rotationally cold (20 K) but vibrationally hot (1200 K) distributions of the NO product. Tetrazine-l,4-dioxde undergoes similar decomposition pathway through (Si/So)ci; however, it produces rotationally hotter (50 K) but vibrationally colder distribution of the NO product. Thus the relative position of the oxygen atoms attached to the tetrazine ring is important parameter along with their nonadiabatic chemistry controlling their final energetic reactivity. Decomposition dynamics of all energetic materials is faster than 180 fs. Considering the influence of conical intersections in the excited electronic state decomposition of energetic materials, rotationally cold N2 product is predicted to be the major decomposition product of high nitrogen content energetic species. The present work infers that generation of internally cold product is an important characteristics of a true energetic molecule. Presence of low lying chemically relevant conical intersections provides a direct pathway of ultrafast decomposition chemistry of energetic molecules. The energy barrier to the low lying chemically relevant conical intersection, in principle, would be a point of interest to make a system more or less energetic.Item Open Access Quantum dot and polymer sensitization of single crystal titanium dioxide electrodes(Colorado State University. Libraries, 2011) Sambur, Justin, author; Parkinson, Bruce A., advisor; Maciel, Gary E., committee member; Elliott, C. Michael, committee member; Van Orden, Alan K., committee member; Marconi, Mario C., committee memberThe morphology of semiconductor nanocrystals or quantum dots (QDs) and conjugated polymers at the interface of TiO2 is expected to play an important role in the electron injection efficiency of mesoporous sensitized solar cells (SSCs). Atomic force microscopy (AFM) and photocurrent spectroscopy were employed to correlate the interfacial morphology of QDs and polymers with the sensitized photocurrent yields on planar TiO2 single crystal electrodes. QDs prepared by the ex situ ligand exchange method, whereby 3-mercaptopropionic acid (MPA)-capped QDs were synthesized and directly adsorbed onto bare TiO2 single crystals, resulted in both reproducible sensitized photocurrents and predominantly single layer surface coverages. Photoluminescence (PL) and photocurrent measurement techniques were simultaneously employed to detect electron injection from QDs to TiO2 for a variety of long and short alkyl chain capping ligands. Quenching of the PL lifetime, often interpreted as a spectroscopic signature for electron transfer, was observed for QDs capped with long chain ligands that do not produce sensitized photocurrent. The ex situ ligand exchange procedure was also utilized to adsorb single layers of MPA-capped CdSe/ZnS core/shell (CS) and PbS QDs onto single crystal TiO2 electrodes. Despite a potential energy barrier for photo-excited carriers in the CdSe core imposed by the wide band gap ZnS shell, type-I CS QDs effectively sensitized single crystal TiO2 electrodes and continued to operate in a regenerative mode in an aerated, corrosive iodide electrolyte for more than 20 h. PbS quantum dots adsorbed on TiO2 single crystals exhibited for the first time hot electron injection from higher QD excited states and absorbed photon-to-current efficiencies greater than 100% due to multiple exciton collection. The nanoscale morphology and photoactivity of conjugated polyelectrolytes (CPEs) deposited from different solvents onto single crystal TiO2 was investigated with atomic force microscopy (AFM) and photocurrent spectroscopy. Absorbed photon-to-current efficiencies approaching 50% were measured for CPE layers as thick as 4 nm on TiO2. The research herein suggests that controlling surface morphology of QD and polymer sensitizers may lead to the development of inexpensive, high-efficiency sensitized solar cells.Item Open Access Rotation of cell surface and dissolved biomolecules examined by fluorescence imaging, time-tagged single-photon counting, and fluorescence depletion anisotropy(Colorado State University. Libraries, 2022) Pace, Jason M., author; Barisas, B. George, advisor; Crans, Debbie C., committee member; Roess, Deborah A., committee member; Van Orden, Alan K., committee memberIn this dissertation, I discuss our studies examining protein rotation both in solution and on single cells. Chapter I gives background on physics of rotational diffusion, the application of these measurements to cellular systems, and a general overview of the field, including a survey of techniques that have been used to measure rotation of membrane proteins. In the next two chapters, I discuss our research on the effect of various cell treatments known to perturb the dynamics of membrane proteins on the rotation of the high-affinity Type I IgE receptor (FcεRI) expressed on RBL-2H3 cells. I investigated effects on receptor rotation resulting from treatment with IgE antibody as well as from four treatments with IgE and an additional agent including DNP-BSA, paraformaldehyde, MβCD, and cytochalasin D. These agents have varied effects that I expect to cause a significant perturbation of the rotational dynamics of the receptor. These effects range from receptor crosslinking by DNP-BSA and paraformaldehyde which would be expected to hinder receptor rotation to effects on membrane cholesterol content and the underlying cytoskeleton in the cases of MβCD and cytochalasin D, the effects of which are more uncertain and thus of particular interest. I have investigated these phenomena using a single-particle fluorescence imaging approach and, alternatively, a time-tagged single photon counting approach. These topics are the subject of Chapters II and III respectively. These two approaches, while both designed with the intent to investigate the rotational dynamics of membrane proteins using fluorescence microscopy, share little in common with regards to their methods of data collection and analysis. The concepts behind them are completely different and they use an entirely different set of analysis programs. Chapter IV consists of a published manuscript entitled "Continuous fluorescence depletion anisotropy measurement of protein rotation" which describes our work using a newly-developed pump-probe technique to examine protein rotation in solution and extends this to single-cell measurements. In the continuous variant of fluorescence depletion anisotropy used here, the intensity and polarization of a laser beam are modulated continuously by a programmed acousto-optic modulator and Pockels cell respectively to produce the desired excitation waveform. We have used this method to examine rotation of eosin conjugates of carbonic anhydrase, BSA, and immunoglobulin G in 90% glycerol at varying temperatures. We have also explored the potential application of this method to single-cell measurements and recorded preliminary results on eosin-IgE-bound FcεRI. Generally, we found good agreement with time-resolved phosphorescence anisotropy measurements of rotation of solution-phase molecules and of cell surface FcεRI. Chapter V discusses future avenues worth exploring which would improve upon the methods presented in Chapters II and III. These include faster cameras to access shorter timescales, gold nanorods to improve the signal-to-noise ratio, and a method to obtain a true anisotropy in a microscope.Item Open Access Simplified membrane-like systems describing the physical behaviors of cholesterol and anti-diabetic drugs(Colorado State University. Libraries, 2013) Trujillo, Alejandro M., author; Crans, Debbie C., advisor; Roess, Deborah A., committee member; Frye, Melinda A., committee member; Van Orden, Alan K., committee memberThis work evaluates the properties contributing to natural membrane permeability by using simplified systems. Absorption mechanisms are a critical step in evaluating the action of orally active drugs. Reverse micelles (RMs) were used as a membrane-like model to analyze the permeation through spectroscopy. The properties exerted by the ligand and ligand substituents were evaluated in the context of membrane permeation. The polydentate ligand of anti diabetic dipicolinatooxvanadium(V) [VO2dipic])-, 2,6-pyridinedicarboxylate (dipic2-) was observed for permeability in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) RMs. Measurements using proton nuclear magnetic resonance (1H NMR) spectroscopy revealed the permeation and hydrophobic stability at physiological pH for dipic2-. Substituents, NH2, OH, H, Cl, NO2 were evaluated forinfluencing the stability and permeability of [VO2(dipic)]-; in AOT RMs. Using infrared spectroscopy (IR), substituent changes significantly influenced the permeation of the vanadium complex series. Properties contributing to the membrane permeation of drugs may also be altered by membrane composition. Cholesterol is present in intestinal membranes and is known to possess properties reducing permeability. A system composed of cetyltrimethylammonium bromide (CTAB), 1-pentanol, cholesterol, and an aqueous phase formed RMs characterized by NMR and dynamic light scattering (DLS). Cholesterol altered the RM structure and proton transfer rates between the water and 1-pentanol of the system. Combined, this work illustrates that ligands, substituents, and membrane components influence the uptake of orally administered drugs.Item Open Access Single-shot flash imaging using a compact soft x-ray microscope(Colorado State University. Libraries, 2012) Carbajo, Sergio, author; Menoni, Carmen S., advisor; Rocca, Jorge J., committee member; Marconi, Mario C., committee member; Krapf, Diego, committee member; Van Orden, Alan K., committee memberMicroscopes extend the ability of our eyes to see objects at micro- and nanoscales. There are applications, however, for which a static image is not sufficient, and thus require information on the dynamics before a process can be understood and controlled. Therefore, the visualization of nanoscale dynamics in real-space can significantly contribute to the understanding of nanoscale processes and to accelerate the development of new nanodevices. Today, there is a need for practical microscopes capable of delivering nanometer spatial resolution and ultrafast temporal resolution in order to readily visualize any arbitrary nanoscale phenomenon. Conventional visible light microscopes can visualize ultrafast dynamics but are inherently limited in spatial resolution to about 200 nm. Alternatively, transmission electron microscopes can routinely provide atomic spatial resolutions of static samples. Probing dynamics is possible using stroboscopic schemes with nanosecond temporal resolution or scanning methods which can obtain femtosecond temporal resolution at the expense of hours-long image acquisition times. Soft x-rays (SXR) microscopes provide the ability to resolve at the nanoscale and at the same time image dynamics with nanosecond to picosecond time resolution. Pioneering work has been carried out using synchrotron illumination that has allowed to study repetitive phenomena in magnetic materials. There are however processes that are statistically reproducible but individually non-recurring that require SXR flash illumination to capture their dynamics. SXR flash imaging requires a large number of photons per pulse to illuminate the sample (about 10E12 photons per pulse). There are two types of SXR sources presently available which offer such high peak brightness: free electron lasers (FEL) and table-top SXR lasers. FELs have been used to probe dynamics using holographic and diffractive imaging configurations. This thesis describes the first demonstration of real-space flash imaging using a compact SXR laser operating at a wavelength of 46.9 nm. A sequence of flash images obtained with the full-field SXR microscope with a spatial resolution of 50 nm and temporal resolution of 1.5 ns captured the interaction dynamics of a rapidly oscillating magnetic tip in close proximity to a magnetized surface. The interaction of the tip and the stray magnetic fields led to changes in the amplitude of the tip oscillation as small as 30 nm. Modeling of the interaction assuming an undamped perturbed harmonic oscillator corroborate the experimental results. The use of compact plasma-based SXR lasers operating at wavelengths down to 10.9 nm will allow to capture flash images and render animations of picosecond phenomena with a few nanometers accuracy on a table-top.Item Open Access Synthesis and characterization of transitional metal polypyridine complex fullerene salts(Colorado State University. Libraries, 2010) Hong, Jie, author; Elliott, C. Michael, advisor; Prieto, Amy Lucia, committee member; Van Orden, Alan K., committee member; Ladanyi, Branka M., committee member; Hochheimer, Hans D., committee memberIn recent years, ionic fullerene (C60) salts have attracted much attention due to their interesting chemical and physical properties. Transition metal polypyridine complex, most notably, tris (2, 2'-bipyridine)ruthenium-based compounds, [RuL3]m+, have a number of photochemical and electrochemical properties which make them of interest for both fundamental and applied studies. The similarity of electrochemical potentials of [RuL3] and C60"’ gives rise to the possibility of a new charge-transfer ionic salts [Ru L3m+]n(C6on-)m- In chapter I, the background of ionic C60 salts as well as the motivation of preparing transition metal polypyridine complex C60 salts is described in detail. A chart of electrochemical data is generated and used as a guideline to predict the possible stoichiometries of ionic salts throughout the whole research work. In Chapter II, the synthesis and characterization of three ionic salts using [Ru(bpy)3]m+ (m = 1, 2) as cations are fully described. All three salts are semiconducting with the highest conductivity at ~ 10 S • m-1. Interesting paramagnetism is reported as well. The detailed discussions based on single crystal and powder X-ray diffraction studies are useful in better understanding the electronic conduction and magnetism. The physical properties of ionic C60 salts can be rationalized based on the crystal packing. In the presence of a bulky cation Ru(bpy)3m+, an expanded crystal lattice is found with weak site-site interactions. In Chapter III, the ligand substitution effect of [RuL3 m+]n(C60n-)m is examined. Four ligands: 4, 4'-dimethyl-2, 2'-bipyridine (4DMB), 5, 5'-dimethyl-2, 2'-bipyridine (5DMB), 4, 4'-di-tert-butyl-2, 2'-bipyridine (TBB) and 4, 4', 5, 5'-tetramethyl-2, 2'- bipyridine (TMB) are chosen as the targets. The ligand substitution not only changes the redox potentials of cation Ru(bpy)3m1 but also alters its size. This provides a route for tuning the properties of [RuL3 ’”^]n(C6on-)m • Electrical and magnetic properties of all compounds as prepared are investigated. The highest conductivity found is also close to 10 S • m-1. In Chapter IV, the effect of substituting ruthenium by chromium in metal complex ionic C60 salts is studied. Cr(bpy)3 m+ and Ru(bpy)3 m+ are very similar in size but of quite different redox potentials. The electrical conductivity of their corresponding ionic salts shows large dependence on the redox potentials.