Thesis (Ph. D.)--Ohio State University, 2006. / Available online via OhioLINK's ETD Center; full text release delayed at author's request until 2009 Aug 16

Thesis (Ph.D.)--Virginia Commonwealth University, 2008. / Title from title-page of electronic thesis. Prepared for: Dept. of Chemisty. Bibliography: leaves 134-141.

Thesis (Ph.D.) - University of Queensland, 1999. / Includes bibliography.

Cis-diol-containing metabolites have attracted increasing attention in recent years. These metabolites widely exist in the body fluids and tissues. They play important roles in the structure, function and metabolic activity of cells. Some of them are related to cell proliferation and metabolic processes. And they have been used to denote a state of disease as potential biomarkers. Several methods have been developed for the analysis of cis-diol-containing metabolites. However, these methods faced a challenge to separate and detect isomers of these compounds, particularly for compounds with low abundance and high polarity. Therefore, novel methods were necessary to improve the separation and detection sensitivity of this kind of metabolites. With this aim, chemical derivatization methods were developed for cis-diol-containing metabolite detection by using liquid chromatography-mass spectrometry in this project. These methods were optimized and validated to achieve the optimal reaction conditions. And they were applied to study real-world biological systems, including the changes of modified nucleosides in hepatocellular carcinoma (HCC) nude mice and toxic effects of bisphenol A (BPA) exposure. Firstly, the derivatization reaction of cis-diol compounds with acetone were optimized. Factors that affected reaction efficiency were investigated by reacting guanosine (G) with acetone. The optimal reaction conditions were validated by detecting four acetonides of urinary nucleosides by using LC-MS/MS. The results showed that the approach had good linearity, accuracy and precision. The recoveries were ranged from 92.9% to 103.5%. It indicated that the assay was reproducible. The robust method should be potentially useful for the analysis of modified nucleosides and other cis-diol-containing metabolites in biological samples. The validated derivatization method was applied to determine urinary nucleosides by LC-MS. This method not only improved the retention of nucleosides on reversed-phase column, but also reduced the matrix effect from urine samples and enhanced detection sensitivity of mass spectrometry. Isotope labeling method with acetone-d6 and multivariate statistical analysis enabled the positive identification of 56 nucleosides, including 52 modified nucleosides. The obtained results indicated that the derivatization method was practical, fast and effective for the identification of urinary nucleosides. It was successfully applied to study the changes of urinary nucleosides in nude mice bearing HCC. Some significantly changed nucleosides were identified as potential biomarkers. Subsequently, this approach was modified by employing parallel reaction monitoring (PRM) method which was based on high resolution MS to detect urinary nucleosides in rats exposed to BPA. Comparing to the data acquired by triple quadrupole MS with neutral loss scanning, higher specificity and sensitivity were achieved by using PRM scanning mode. Therefore, more nucleosides were identified by using the method in urine samples (from 56 up to 66). The changes of the detected nucleosides were studied in the rats exposed to BPA. Various trends of modified nucleosides were observed with different dose BPA exposure. Specifically, the high-dose exposure group was the most strongly affected. The biomarker of RNA oxidation, 8-hydroxyguanosine (8-oxoG), showed significant change in this group. It proved that BPA exposure could induce RNA damage when the dose of BPA was beyond a certain amount. Except for nucleosides, other cis-diol-containing metabolites, such as carbohydrates, were also studied by using the derivatization method. Acetone and acetone-d6 were applied to label the cis-diol metabolites. Based on the chemical isotope labeling, cis-diol metabolites were easily recognized from urine samples. Influence of BPA exposure on these metabolites was investigated by comparing different doses of BPA administration on rats. Analytes showed noticeable difference were highlighted. Pathway analysis indicated that galactose metabolism, nucleoside and its analogues metabolism were disturbed. The derivatization method was extended to quantify nucleotides in plasma samples. According to the specific physical-chemical properties of nucleotides, the method was improved to fit the requirement of analysis by using 1,1-Dimethoxycyclohexane (DMCH) as derivatization agent and formic acid (FA) as catalyst. Tip micro-columns packed with TiO2 were used for selective adsorption of nucleotides in the plasma. Then in-situ derivatization were carried out to change the polarity of targeted compounds. LC-MS analysis of the derivatization products were employed without using ion-pairing reagents. This method exhibited a high selectivity for the extraction of nucleotides. After derivatization, retention of nucleotides on reversed-phase C18 column was improved. Complete separation of nucleotides with the same base was achieved. The peak shape was symmetrical and the tailing was eliminated by using high pH mobile phase. The method settled the problems of nucleotide detection, which were poor retention, trailing, in-source fragmentation and contamination of ion-pairing reagents. The quantitative method was successfully applied to determine the content of nucleotides in plasma samples of rats exposed to BPA. It was simple and fast, as well as good selectivity and stability. It could be extended to detection of other phosphorylated metabolites with similar structure. To our best knowledge, it was the first time to employ derivatization methods to detect cis-diol-containing metabolites. The methods decreased the matrix effects of complex biological samples, and also decreased the polarity of cis-diol-containing metabolites. The changes of properties not only improved the chromatographic separation, but also enhanced the MS intensities. The methods overcame the problems of cis-diol-containing metabolite detection on reversed-phase column. They were successfully applied to study the changes of cis-diol-containing metabolites of HCC and toxic effects of BPA exposure. The method might be extended to determine other cis-diol-containing metabolites in urine samples as well as in cells, tissues and plasma samples. It might be valuable for the understanding of the roles of cis-diol-containing metabolites in in cell metabolism.

<p> An inexpensive method was developed for the conversion of a high performance liquid chromatography (HPLC) system for use with 1 mm I.D. microbore columns. Chromatographic performance of the system was tested under both isocratic and gradient elution conditions, using a standard mixture of 16 polycyclic aromatic hydrocarbons (PAH).</p> <p> The microbore column HPLC was also coupled to a mass spectrometer equipped with a moving belt interface. Chromatographic performance under isocratic and gradient elution and mass spectral performance under scanning and selected ion monitoring modes were tested using the PAH standard.</p> <p> A marine sediment extract was subjected to qualitative and quantitative analysis for PAH. Qualitative results on the sample were obtained from a combination of retention indices, mass spectra, and retention times. Quantitation was performed by microbore column liquid chromatography-mass spectrometry (LC/MS) in the selected ion monitoring mode of operation. The method of calibration used was external calibration.</p> <p> The microbore column HPLC system exhibited good chromatographic behavior. Resolution, peak shape and short term retention time reproducibility were good, although, long term retention time fluctuations, due to changing mobile phase flow rates, were noted.</p> <p> The combination of microbore column HPLC with a moving belt interface and mass spectrometer gave excellent results. Problems commonly encountered with conventional column (4.6 mm I.D.) LC/MS, such as backstreaming, droplet formation, and splattering were greatly reduced, resulting in no apparent loss of chromatographic integrity and stable mass spectrometer operating conditions. These operating conditions proved to be most advantageous in the quantitative analysis of the marine sediment extract by selected ion monitoring.</p> / Thesis / Master of Science (MSc)

Neuropathic pain is defined as "pain initiated or caused by a primary lesion or dysfunction in the nervous system". In contrast to physiological pain that warns of noxious stimuli likely to result in tissue damage, neuropathic pain serves no protective function. Examples of neuropathic pain states include postherpetic neuralgia (shingles) and phantom limb / stump pain. This pain state also exists in the orofacial region, with the possibility of several variants including atypical odontalgia and burning mouth syndrome. There is a paucity of information on the prevalence of neuropathic pain in the orofacial region. One study assessed patients following endodontic treatment and found that approximately 3 to 6percent of patients reported persistent pain. Patients predisposed to the condition atypical odontalgia (phantom tooth pain) include those suffering from recurrent cluster or migraine headaches. Biochemical and neurobiological processes leading to a neuropathic pain state are complex and involve peripheral sensitisation, and neuronal plasticity of the central and peripheral nervous systems. Subsequent associated pathophysiology includes regional muscle spasm, sympathetic hyperfunction, and centralisation of pain. The relevant clinical features of neuropathic pain are: (i) precipitating factors such as trauma or disease (infection), (ii) pain that is frequently described as having burning, paroxysmal, and lancinating or sharp qualities, and (iii) physical examination may indicate hyperalgesia, allodynia and sympathetic hyperfunction. The typical patient complains of persistent, severe pain, yet there are no clearly identifiable clinical or radiographic abnormalities. Often, due to the chronicity of the problem, afflicted patients exhibit significant distress and are poor pain historians, thus complicating the clinician's task of obtaining a detailed and relevant clinical and psychosocial history. An appropriate analgetic blockade test for intraoral sites of neuropathic pain is mucosal application of topical anaesthetics. Other, more specific, tests include placebo controlled lignocaine infusions for assessing neuropathic pain, and placebo controlled phentolamine infusions for sympathetically maintained pain. The treatment and management of neuropathic pain is multidisciplinary. Medication rationalisation utilises first-line antineuropathic drugs including tricyclic antidepressants, and possibly an anticonvulsant. Topical applications of capsaicin to the gingivae and oral mucosa are a simple and effective treatment. Neuropathic pain responds poorly to opioid medication. Psychological assessment is often crucial in developing strategies for pain management. Psychological variables include distress, depression, expectations of treatment, motivation to improve, and background environmental factors. To enable a greater understanding of neuropathic pain, thereby leading to improved treatments, high-performance liquid chromatography-mass spectrometry is one analytical technique that has the potential to contribute to our knowledge base. This technique allows drugs and endogenous substances to be assayed from one sample in a relatively short time. The technique can identify, confirm, and measure the concentrations of multiple analytes from a single sample.

Along with genes and proteins, metabolites play important roles in sustaining life. There remains much to be learned about the in vivo roles of metabolites. Metabolomics is a comparative tool to study global metabolite levels in samples under various conditions. This dissertation describes the development and application of metabolomics strategies for discovery of biologically active or novel metabolites with priori knowledge about genes, proteins, or phenotypes. The power of metabolomics for discovery of novel metabolites from genes is demonstrated through the work with the pyochelin (pch) gene cluster. Comparison of the extracellular metabolomes of pch gene cluster mutants to the wild-type Pseudomonas aeruginosa (strain PA14) identified 198 ions regulated by the pch genes. In addition to known metabolites, a pair of novel metabolites were characterized as 2-alkyl-4,5-dihydrothiazole-4-carboxylates (ATCs). Subsequent assays revealed that ATCs bind iron and that their production is regulated by iron levels and dependent on pchE gene in the pch gene cluster. Metabolomics can also facilitate discovery of active metabolites from proteins, as shown in the work with orphan nuclear receptor Nur77. We applied a metabolomics platform for detected protein-metabolite interactions to identify lipids that bind to Nur77. Using this approach, we discovered that the Nur77 ligand-binding domain (Nur77LBD) enriched unsaturated fatty acids (UFAs) in tissue lipid mixtures. Subsequent biophysical and biochemical assays indicate that UFAs bind to Nur77LBD to cause changes in the conformation and oligomerization of the receptor. Last, analogous to classic fractionation experiments, metabolomics can also be applied to discover active metabolites from phenotypes. Using combination of genetics, biochemistry, and metabolomics, we identified three phenazine compounds produced by Pseudomonas aeruginosa that are toxic to the nematode Caenorhabditis elegans. 1-hydroxyphenazine, phenazine-1-carboxylic acid (PCA), and pyocyanin are capable of killing nematodes in a matter of hours. 1-hydroxyphenazine is toxic over a wide pH range, whereas the toxicities of PCA and pyocyanin are strictly pH-dependent at non-overlapping pH ranges. The diversity within a class of metabolites can be used to modulate bacterial toxicity in different environmental niches. / Chemistry and Chemical Biology

Neuropathic pain is defined as "pain initiated or caused by a primary lesion or dysfunction in the nervous system". In contrast to physiological pain that warns of noxious stimuli likely to result in tissue damage, neuropathic pain serves no protective function. Examples of neuropathic pain states include postherpetic neuralgia (shingles) and phantom limb / stump pain. This pain state also exists in the orofacial region, with the possibility of several variants including atypical odontalgia and burning mouth syndrome. There is a paucity of information on the prevalence of neuropathic pain in the orofacial region. One study assessed patients following endodontic treatment and found that approximately 3 to 6percent of patients reported persistent pain. Patients predisposed to the condition atypical odontalgia (phantom tooth pain) include those suffering from recurrent cluster or migraine headaches. Biochemical and neurobiological processes leading to a neuropathic pain state are complex and involve peripheral sensitisation, and neuronal plasticity of the central and peripheral nervous systems. Subsequent associated pathophysiology includes regional muscle spasm, sympathetic hyperfunction, and centralisation of pain. The relevant clinical features of neuropathic pain are: (i) precipitating factors such as trauma or disease (infection), (ii) pain that is frequently described as having burning, paroxysmal, and lancinating or sharp qualities, and (iii) physical examination may indicate hyperalgesia, allodynia and sympathetic hyperfunction. The typical patient complains of persistent, severe pain, yet there are no clearly identifiable clinical or radiographic abnormalities. Often, due to the chronicity of the problem, afflicted patients exhibit significant distress and are poor pain historians, thus complicating the clinician's task of obtaining a detailed and relevant clinical and psychosocial history. An appropriate analgetic blockade test for intraoral sites of neuropathic pain is mucosal application of topical anaesthetics. Other, more specific, tests include placebo controlled lignocaine infusions for assessing neuropathic pain, and placebo controlled phentolamine infusions for sympathetically maintained pain. The treatment and management of neuropathic pain is multidisciplinary. Medication rationalisation utilises first-line antineuropathic drugs including tricyclic antidepressants, and possibly an anticonvulsant. Topical applications of capsaicin to the gingivae and oral mucosa are a simple and effective treatment. Neuropathic pain responds poorly to opioid medication. Psychological assessment is often crucial in developing strategies for pain management. Psychological variables include distress, depression, expectations of treatment, motivation to improve, and background environmental factors. To enable a greater understanding of neuropathic pain, thereby leading to improved treatments, high-performance liquid chromatography-mass spectrometry is one analytical technique that has the potential to contribute to our knowledge base. This technique allows drugs and endogenous substances to be assayed from one sample in a relatively short time. The technique can identify, confirm, and measure the concentrations of multiple analytes from a single sample.

Thesis (M.S.)--Villanova University, 2008. / Chemistry Dept. Includes bibliographical references.

Thesis (Ph. D.)--Cleveland State University, 2009. / Abstract. Title from PDF t.p. (viewed July 29, 2009). Includes bibliographical references (p. 105). Available online via the OhioLINK ETD Center and also available in print.