The combination of metal catalyzed oxidation (MCO) reactions and mass spectrometry (MS) is a relatively new method of determining the coordination structure of metalloproteins. The sensitivity of the MCO/MS method gives it significant potential for the study of protein structure. The method takes advantage of Fenton-type oxidation reactions occurring at protein-bound transition-metal ions. These reactions produce reactive oxygen species that modify metal binding residues, and the modified residues are identified using the peptide sequencing ability of MS. This dissertation focuses on increasing the reliability and versatility of the MCO/MS method as a tool for studying metal-protein interactions. The importance of ascorbate concentration in controlling the oxidation yield and specificity of the MCO reactions has been established, and sodium persulfate has been identified as a specific and potent oxidant. Greater insight into the role of ascorbate has allowed us to develop a new "detuned" version of MCO/MS method that can oxidize residues beyond the metal-binding site, making the method more sensitive to minor changes in protein structure that might occur upon metal binding to a protein. Application of the detuned method to Cu binding of β-2-microglobulin suggests some possible structural changes caused by metal binding that might provide insight into the amyloid formation of this protein. The versatility of the MCO/MS approach has been expanded by, improving the speed of the method and extending its application to other metals. In an effort to better study dynamic systems, microwave irradiation has been used to decrease the time required for MCO reactions by a factor of 10. The utility of the MCO/MS method for the study of non-Cu transition metal systems has been illustrated by determining suitable MCO reaction conditions for peptides that bind Mn, Fe, Co and Ni and a whole protein, Nickel superoxide dismutase. Finally, we have studied the effect of amino acid oxidation on the dissociation patterns of peptide ions during tandem MS (MS/MS) experiments and the identification of binding residues. We have found that histidine oxidation changes the peptides dissociation pattern. We demonstrate that an N-terminal derivatization method can be used to simplify the MS/MS interpretation in such circumstances.

Crucial parameters affecting protein-polyelectrolyte complexation include protein charge anisotropy, chain flexibility and polyelectrolyte (PE) charge sequence distribution. PE chain flexibility was found to affect the colloid-binding affinity: stiffer PE's binding more strongly than flexible PEs. However, the definition of chain stiffness should not be conflated with polyelectrolyte persistence length especially in the cases corresponding to the resistance of the chain to bending. A Monte Carlo study of the PE binding site coupled with protein electrostatic potential modeling has further clarified these issues by identifying the nonspecific polyelectrolyte binding site on serum albumin at conditions corresponding to experiments. Examination of the binding between serum albumin and decamers of acrylamidopropanesulfonate and acrylamide of different sequences has shown that the bound decamer retains much of its configurational entropy. Polyelectrolyte stiffness and charge sequences have profound effects on the formation of polyelectrolyte-protein coacervates, as shown by comparison of coacervates made with chitosan vs. those made with a more flexible and fully charged synthetic PE of the same structural charge density. The coacervates with chitosan differ markedly in rheology and dynamic light scattering, and SANS. These differences are explained in the context of a model in which coacervates contain protein-rich dense domains with sizes > than a few hundred nanometers. This model has been supported by fluorescence recovery after photobleaching, CryoTEM and pulsed field gradient NMR. In the context of this model, chain flexibility and the charges of ca, 50 nm polyelectrolyte-protein aggregates have been shown to affect the connectivity and size of the dense domains, which behave as transient obstacles to protein diffusion within the coacervates.

The primary route most cells utilize to acquire iron is the human serum transferrin (hTf)-human transferrin receptor (TfR) mediated uptake pathway. This pathway has been exploited in the treatment of tumor cells; therefore it is vital to understand the interactions between hTf and TfR at the cell surface (pH 7.4) and in the endosome (pH 5.6). The present study investigates the role of iron in hTf binding to TfR to determine whether iron free (apo) hTf can bind TfR at pH 8.3 and understand the conformational changes (associated with iron release) in hTf-TfR at pH 5.6. Electrospray ionization mass spectrometry (ESI-MS) was used to detect the binding products of competitive, single and displacement assays between different forms of hTf (apo, monoferric, diferric) or lobe fragments and TfR at pH 8.3 and 5.6. All of the hTf-bound TfR in a specific but reversible manner at basic and acidic pH. At pH 8.3, diferric (holo)-hTf was the preferred ligand for TfR followed by monoferric-hTf and then apo-hTf. The iron-free lobe of monoferric-hTf was stabilized by the iron-bound lobe (interlobe communication) whereas the apo-hTf was stabilized by the glycan moieties on the C-terminal lobe (C-lobe). Binding assays performed with the lobe fragments suggest the C-lobe of hTf initially binds TfR, which induces allosteric conformational changes resulting in the binding of the N-lobe. However, the latter is incapable of binding TfR on its own. At pH 5.6, apo-hTf and FeNTf (iron in the N-lobe) were the preferred TfR ligands followed by Fe2Tf and FeCTf (iron in the C-lobe). Therefore, iron status of the C-lobe dictated the binding stability to TfR at pH 5.6. When the C-lobe contains iron it cannot completely open, as required for stable TfR binding at pH 5.6; iron occupancy of the N-lobe had no affect on the interaction due to the lack of binding to TfR when the C-lobe has an open conformation.

No description available.

Fertility decline in Zimbabwe has been driven by an increase in the contraceptive prevalence rate (CPR). However, adolescent childbearing remains a challenge. Adolescent fertility increased from 103 births per 1 000 women in 1988 to 110 births per 1 000 women in 2015. The study aims to examine the trends in contraceptive use, unmet need, method choice, and determinants of contraceptive use and method choice among young women aged 15-24 in Zimbabwe from 1988 to 2015. The study utilises six cross-sectional data sets obtained from the Zimbabwe Demographic and Health Survey (ZDHS) for the years 1988, 1994, 1999, 2005-06, 2010-11, and 2015. Descriptive statistics and multivariate logistic regression were used to achieve the objectives of the study. Results showed that young women are sexually active and mostly outside of marital union. The use of modern contraceptives among sexually active young women increased from 39.7% in 1988 to 58.2% in 2015. Unmet need for modern contraceptives declined from 54.1% in 1994 to 41.6% in 2015. The pill remains the most common method used, and the use of injections and implants has also increased over time. The results show that young women aged 22-24, residing in urban areas, better educated, employed, married or cohabitating, with one or more living children, and those with a desire to have more children after 2 years are more likely to use modern contraceptives compared to other groups. Whereas, widowed, divorced, or separated, and women with a desire to have more children within 2 years are less likely to use modern contraceptives. Young women who are married (OR=2.265), better educated (OR=1.590), and have one or more living children (OR=18.411) are more likely to use injections compared to other groups. Women with secondary or higher education (OR = 2.748) and one or more living children (OR= 22.673) are more likely to use Norplant/Implants compared to other groups. In conclusion, the study demonstrates that young women are sexually active and the unmet need for modern contraceptives remains a challenge. The use of contraceptives is associated with age group, residence, education level, employment status, marital status, parity, and desire for more children. There is need to strengthen young women's universal access to family planning information and services.

There currently exists no commercialized method for rapid sampling and analysis of trace tar ingas streams. Solid phase microextraction (SPME) with a polydimethylsiloxane (PDMS) solidphase has been previously investigated as a possible candidate due to its solvent-free natureand reusability. This project set out to deliver a proof of concept study to test whether SPMEcan be sufficiently tuned to analyse trace tar content in syngas below the concentration of 0.1mg/Nm 3 . Due to complications that arose from the Covid-19 pandemic, it was unfeasible tocarry out the practical elements of the project. Instead a concept design for carrying out such astudy has been successfully developed. This design envisions a two-chamber setup able tosample syngas directly from a gasifier at 60 °C and 125 °C respectively and is illustrated in thetext. It utilizes commercially available solvent tubes to cross-check and verify the SPME results. / I nuläget finns det ingen kommersiell metod för att snabbt extrahera och analysera spår av tjärkomponenteri gasströmmar. Tidigare har solid phase microextraction (SPME) medpolydimetylsiloxan (PDMS) som fast fas undersökts som en möjlig kandidat då den ej kräverlösningsmedel och kan enkelt återanvändas. Detta projekt hade som mål att bevisa att SPMEkan anpassas tillräckligt känsligt för att analysera spår av tjära i syngas med en koncentration påmindre än 0,1 mg/Nm 3 . På grund av komplikationer som uppstod i samband med Covid-19pandemin var det inte möjligt att utföra den praktiska delen av projektet. Istället så har endesign tagits fram för ett koncept som beskriver hur man kan genomföra den praktiska delen.Designen beskriver en två-kammare lösning som kan användas för att ta prover från syngas somkommer direkt från en förgasare. Proverna tas vid temperaturer om 60 °C och 125 °C för attuppnå maximal känslighet. En uppsättning kommersiellt tillgängliga sorbentrör används för attkontrollera resultaten från SPME.

Paper Based Microfluidic Devices (microPADs) are a new platform for point-of-care diagnostic assays for use in resource-limited settings. These devices rely typically on enzymatic assays to produce their results, which makes them susceptible to degradation when exposed to extreme environmental conditions such as high temperature. In order to overcome this limitation, this research project focused on investigating the use of polymers instead of enzymes to detect analytes on microPADs. Polymer-bound boronic acid, a glucose and pH sensitive polymer, was incorporated into microPADs in order to develop a chronometric, paper-based glucose assay. The polymer was tested with both lateral and vertical flow microPADs made from three different types of paper, and several different methods of incorporating the polymer into the devices were also explored. While some devices appeared to show a trend in signal versus concentration of glucose, none of the results were statistically significant due to the large standard deviations in the signal. Upon further analysis of the results, the overall conclusion was that the devices were not sensitive enough to detect glucose in the range of concentrations that would be practical for clinical diagnostic applications.

Release of petroleum products, in particular gasoline, at underground storage tank facilities is a significant source of groundwater contaminants. These products are highly complex and variable mixtures of organic compounds. This makes their residue analysis in environmental samples and evaluation of their solubility behavior difficult. Research efforts described in this work addressed development of a rapid analytical method for petroleum product residues in water and evaluation of gasoline aqueous solubility behavior. Analytical method development focussed on capillary GC/FID and GC/MS with direct aqueous injection (DAI). Excellent chromatographic performance for C1 to C4 alcohols, C6 to C9 monoaromatics, phenols and other compounds was achieved. Calibration curves were linear over a wide dynamic range and analytical limits of detection of key analytes like benzene and toluene, while higher than LOD's obtained with other methods, were below established Maximum Contaminant Levels. The method was found to be simple, rapid, comprehensive and sufficiently sensitive for monitoring drinking water quality. With this method, the water solubility behavior of four gasolines spanning a wide range in composition was investigated. Highly water soluble gasoline constituents (alcohols, phenols, methyl tert-butyl ether) were found to have effective dissolution velocities which were greater than common aromatic compounds like benzene and toluene. It was also found that fuel-water partition coefficients of various gasoline constituents could be approximated by assuming ideal Raoult's Law behavior without making appreciable errors in estimates in solute concentrations. Deviation from the ideal was relatively small even with a product containing 85 percent (v/v) methanol. Finally, successive batch equilibrations of the products with water showed that alcohols, phenols, MTBE and other gasoline constituents which have water solubility are leached rapidly from the product phase. As a result, any cosolvent effects on petroleum hydrocarbon solubility will be attenuated rapidly following a product release and the onset of leaching of contaminated soil.

Trace impurity determinations in volatile, pyrophoric organometallic materials is complicated owing to its chemical nature. Furthermore, trends toward high semiconductor circuit density demand that impurity determinations are performed at increasingly low levels. Volatility of the impurities is also desired as it plays a significant role in impurity incorporation in semiconductor products. Determination of both volatile and nonvolatile impurities in semiconductor-grade organometallic reagent materials has been accomplished using electrothermal vaporization - inductively coupled plasma spectrometry. Solid or liquid materials can be dispensed directly onto a graphite microboat, and application of an appropriate time-temperature ramp allows separation of impurities based on volatility. Temporal separation allows quantitative capabilities on both volatile and nonvolatile signals in a single ETV run. Calibration efforts for volatile impurities have been compared with results from exponential dilution and direct vapor sampling techniques. Nonvolatile impurity determinations can be reasonably performed with aqueous external standard calibration. Inductively coupled plasma-mass spectrometry provides an alternate and more sensitive, multielement detection method. Several spectroscopic and non-spectroscopic difficulties with volatile impurity detection remain. Nonetheless, qualitative and semi-quantitative ($<$50% RSD) determination of most impurities may be performed in a single ETV run.

No description available.