In this project, “selected ion flow tube mass spectrometry” (SIFT-MS), a sensitive analytical technique, reveals potential for the development of applications in the environment and petroleum areas. Many prior applications have shown their potential for analyzing samples in widely disparate areas. Its fast analysis process and high sensitivity gives it a significant advantage over more conventional methods. This project is directed at expanding this technology to more applications in the petroleum and air quality areas. The application to the petroleum industry has shown that SIFT-MS can quantify H2S and CH3SH in natural gas to 11.8 and 1.2 ppbv, respectively. The SIFT-MS results showed a good linear response with increasing sulfide concentrations by using the H3O+ reagent ion to quantify H2S, CH3SH, and the total combined concentration of DMS and C2H5SH. The ability to use the SIFT-MS instrument to trace chemical tracers, such as bromobenzene and chlorobenzene in hydrocarbon mediums, was also investigated. SIFT-MS showed also the capacity to trace these compounds in natural gas and LPG. The limits of detection (LOD) were also obtained. This study furthermore, found the utility of the NO+ reagent ion to analyse qualitatively some of the large hydrocarbons. Unfortunately, however, the SIFT-MS reactions could not distinguish between the structural isomers of these aromatic and aliphatic hydrocarbons and there was probable conflict between the fragmentation product ions with smaller hydrocarbons. From the air quality perspective, the SIFT-MS also proved its potential for use in air monitoring, using passive techniques and particularly for BTEX (benzene, toluene, ethyl benzene, and xylene) compounds. The study illustrated SIFT-MS’s ability to deal with thermal desorption and passive methodology in general. Ecan (Environmental Canterbury) routinely examines environmental pollutants in Christchurch air by passive sampling methodologies. In this study, we compared and achieved agreement by comparing the result of thermal desorption-SIFT-MS (TD-SIFT-MS) of Christchurch air with the more conventional methodologies of TD-GC-MS and the Ecan agency measurements.

Gap junctions are communicating junctions between cells that allow small molecules to pass from the cytoplasm of one cell to the cytoplasm of an adjacent cell. The pores of gap junctions are comprised of two adjacent connexons on neighboring cells, and each connexon is comprised of six connexin proteins. The eye lens of vertebrates is an avascular tissue that is dependent on gap junctions for the distribution of nutrients as well as the removal of waste products. In addition, as the lens cells develop into fibers, they lose their intracellular organelles including the membrane-bound organelles, and are highly dependent on connexons for movement of metabolites and waste materials. Only two connexins, in Bos Taurus Cx44 and Cx49, are highly expressed in lens fiber cells. Thus, the lens offers an excellent system for studying gap junctions. In this study, high-pressure liquid chromatography (HPLC) and mass spectrometry (MS) techniques were used to isolate and characterize connexin proteins from the eye lens of the cow and mouse. Despite over 300 proteins being identified from bovine lens using MS techniques, it was still possible to identify the two connexin proteins following proteolytic digests and MS analysis of the resultant peptides. Several post- translational modifications (PTMs) were identified and characterized in lens fiber connexins, including phosphorylations, acetylations and deamidations and proteolytic cleavages. Changes in phosphorylation of several other lens proteins upon the activation of protein kinase C were also identified. Detection of the orthologous proteins in mouse lens proved more challenging, but peptides derived from both connexin proteins were also detected from this tissue and PTMs of mouse connexins were also observed. Glutathione-S-transferase fusions to mouse Cx44 and Cx50 were used to identify a number of proteins that may interact with the mouse connexins, and the relevance of those interactions was considered. The utility of mass spectrometry to the identification of specific proteins from complex mixtures was clearly demonstrated, and its application to understanding the functional relevance of PTMs was discussed.

No description available.

No description available.

Gap junctions are communicating junctions between cells that allow small molecules to pass from the cytoplasm of one cell to the cytoplasm of an adjacent cell. The pores of gap junctions are comprised of two adjacent connexons on neighboring cells, and each connexon is comprised of six connexin proteins. The eye lens of vertebrates is an avascular tissue that is dependent on gap junctions for the distribution of nutrients as well as the removal of waste products. In addition, as the lens cells develop into fibers, they lose their intracellular organelles including the membrane-bound organelles, and are highly dependent on connexons for movement of metabolites and waste materials. Only two connexins, in Bos Taurus Cx44 and Cx49, are highly expressed in lens fiber cells. Thus, the lens offers an excellent system for studying gap junctions. In this study, high-pressure liquid chromatography (HPLC) and mass spectrometry (MS) techniques were used to isolate and characterize connexin proteins from the eye lens of the cow and mouse. Despite over 300 proteins being identified from bovine lens using MS techniques, it was still possible to identify the two connexin proteins following proteolytic digests and MS analysis of the resultant peptides. Several post- translational modifications (PTMs) were identified and characterized in lens fiber connexins, including phosphorylations, acetylations and deamidations and proteolytic cleavages. Changes in phosphorylation of several other lens proteins upon the activation of protein kinase C were also identified. Detection of the orthologous proteins in mouse lens proved more challenging, but peptides derived from both connexin proteins were also detected from this tissue and PTMs of mouse connexins were also observed. Glutathione-S-transferase fusions to mouse Cx44 and Cx50 were used to identify a number of proteins that may interact with the mouse connexins, and the relevance of those interactions was considered. The utility of mass spectrometry to the identification of specific proteins from complex mixtures was clearly demonstrated, and its application to understanding the functional relevance of PTMs was discussed.

The three dimensional structure of a protein is important for its function. When misfolded, a protein may be rendered inactive or adapt a conformation that could be toxic. Studying protein folding requires an understanding of protein conformation. Traditionally, protein conformation has been studied using x-ray crystallography and nuclear magnetic resonance (NMR). X-ray crystallography is limited in the analysis of crystallized proteins and is computationally intensive. NMR deals with proteins in solution but reports only an average of conformation and the technique severely suffers from spectral overlapping due to the thousands of resonances of the protein. More recently, mass spectrometry has been employed not only to elucidate primary structures but also gather information on the three-dimensional conformation of proteins. In this study, a mass spectrometric-based approach is used to study the changes in conformation of cytochrome c and the green fluorescent protein when subjected to aqueous-organic solvent systems. The technique involved trypsin digestion and generation of peptide mass maps. For cytochrome c, the experiments were done with ethanol, methanol and acetonitrile to gain insights on naturation and denaturation. An apparent solvent effect to the rate of digestion and propensity for missed cleavages attributed to weakening of hydrophobic interactions and strengthening of intramolecular hydrogen bonding was observed. For the green fluorescent protein, sulfolane, a known supercharging agent, was used to gain insights on the effect of supercharging to protein conformation. Addition of 2.0% sulfolane shifted the charge state envelope of the protein towards lower m/z while adding lower amounts of sulfolane enhanced lower charge states while broadening the charge state envelope. The time course study showed different patterns of digestion dependent on solvent conditions implying changes in conformation. Furthermore, absorbance and fluorescence measurements suggested that addition of sulfolane protects the fluorophore from quenching. The activity of trypsin is not affected by addition of low amounts of sulfolane.

A high frequency, large amplitude helium filled RFQ (Radio Frequency Quadrupole) beam cooler and buncher was developed and tested for use in the TITAN (TRIUMF's Ion Trap for Atomic and Nuclear science) Penning trap mass spectrometer facility. This device will cool and bunch radioactive ion beams for use in TITAN's high precision mass measurements of short-lived isotopes and other experiments. A test stand was built to test the transmission and properties of ions from a surface ion source through injection optics, the linear Paul trap RFQ and the extraction optics in both continuous and pulsed modes. The efficiency of the device was determined to be on the order of 60% in continuous mode. The present measurements confirm a transverse emittance of the extracted beam in bunched mode operation of 4 pi-mm-mrad at an extraction energy of 4 keV.

The measurement of the distribution of kinetic energy carried by neutron particles is of interest to the health physics and radiation protection industry. Neutron particle spectral fluence is essential to the calculation of absorbed dose, equivalent dose, and other dosimetric quantities . Current methods of neutron spectrometry require either a large number of individual measurements and a priori spectral information, or complex and delicate equipment. To reduce these deficiencies, a novel neutron spectrometer, consisting of plastic scintillating fibers in a hexagonal array, was simulated via Monte Carlo. Fiber size and boron content were varied to optimize response characteristics. The results were compared to industry standard multi-sphere spectrometers. Of the geometries and materials analyzed, it was found that smaller diameter fibers with 1% loading of natural boron provide the best efficiency and energy resolution. Energy resolution was found to be similar to multi-sphere spectrometers, with the ability to differentiate on the order of ten energy fluence groups. Near isotropic angular response was traded for significantly reduced detection time and increased simplicity. Spectral analysis of individual fiber response can provide directional information based on the ratio of energy deposition by thermal neutrons to all neutrons. Future work using proton recoil spectral data from individual fibers will allow increases in energy resolution while reducing or eliminating the need for a priori spectral information.

New measurements of the masses of the isotopes⁸,⁹,¹¹Li were made using recently commissioned TITAN Penning trap mass spectrometer at TRIUMF. The measurement of the halo nucleus ¹¹Li represents a new standard in Penning trap mass spectrometry, as it is the shortest lived, t₁/₂ = 8.8 ms, isotope ever weighed using this technique. Low energy, E = 20 keV, beams of these radioactive isotopes were produced using the ISAC facility. These were subsequentlycooled and bunched using a square-wave-driven Radio- Frequency Quadrupole (RFQ) ion guide, which was filled with hydrogen gas. The cooled ion bunches were then passed into a Penning trap where the mass measurements were made. A description of the RFQ in the ISAC hall is given along with some results from the commissioning of the device. A new set of harmonic deceleration optics is presented which have been successfully used to inject ions into the RFQ. Cooling of lithium ions with high DC efficiencies of 20%, in helium, and 40%, in hydrogen, are shown. Extraction of extremely short ion bunches, 30 ns FWHM, is also demonstrated. Storage times for stable lithium ions in helium and hydrogen were investigated. It was found that lithium ions could be cooled in hydrogen for up to 30 ms without significant losses whereas cooling in helium lead to exponential losses with a half-life of 5.7(1)ms. The TITAN Penning trap is described and the ⁸,⁹,¹¹Li data presented. Final values for the mass excess of ∆(⁸Li) = 20945.70(38) keV, ∆(⁹Li) = 24954.80(60) keV and ∆(¹¹Li) = 40728.1(12) keV are obtained. The ⁹,¹¹Li results are then used to obtain a new value for two neutron separation energy of ¹¹Li, S₂n = 369.3(1.3) keV. This agrees with the recent measurement from the MISTRAL spectrometer, 376(5) keV, at the two sigma level, but shows over three standard deviations from the most recent atomic mass evaluation, 300(20) keV

Thesis (PhDAppliedScience)--University of South Australia, 2002.