Thesis (M.Med.Sc.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 53-61). Also available in print.

Thesis (Ph. D.)--University of Rhode Island, 2006. / Includes bibliographical references (leaves 88-91).

In order to study quantitatively the acidity of very weak acids and at the same time the effect of a polar aprotic solvent on the basicity of hydroxide ion a Hammett H_ acidity function based on the ionization of 24 substituted anilines and diphenylamines has been established in the system dimethylsulfoxide-water-tetramethylammonium hydroxide. The basicity of hydroxide ion is increased dramatically as the solvent is changed from water to dimethylsulfoxide. The H_ of a 0.011 molar solution of tetramethylammonium hydroxide ranges from 12 in water to 26 in 99.6 mole % dimethylsul-foxide-water, an increase in basicity of fourteen powers of ten. The increase in basicity is due to the increased activity of the hydroxide ion brought about by the reduction in its solvation in the poor anion-solvating solvent, dimethyl sulfoxide and indicates the extensive solvation enjoyed by the hydroxide ion in water. The pKHA values of the indicator acids vary from 13.84 for 2,4-dinitrodiphenylamine to 25.63 for 3-chloroaniline. From a plot of log KHA versus Hammett substituent constants ( ϭ) for six monosubstituted diphenylamines a rho (ρ) value of 4.07 is found. The magnitude of substituent effects on the acidity of aniline appears to be quite similar. The acidities of all the substituted diphenylamines do not follow the above mentioned correlation with Hammett ϭconstants; the pKHA values of 4-amino-, 4-methoxy-, 4-methylsulfonyl-, and 4-nitrodiphenylamine are all less than expected from the Hammett ϭ constants for the substituents in these compounds. The 4-nitro substituent exerts a particularly large acid-strengthening effect on the acidities of aniline and diphenyl amine; the decreases in pKHA being approximately 8.4 and 6.8 pK units, respectively. The pKHA values of 17 compounds other than those indicators used to establish the H_ function have been determined with the aid of the H_ function. Most of these compounds are alkyl-substituted 4-nitroanilines. Alkyl groups ortho to the amino group of 4-nitroaniline cause a decrease in the pKHA (an increase in acidity). Similarly, N-methyl-, N-ethyl-, and N-isopropyl-4-mitro- aniline are all stronger acids than 4-nitroaniline itself. An explanation for the effects of alkyl substituents on the acidity of 4-nitroaniline in terms of the solvation of both the ionized and unionized amines is advanced. A Hammett Hₒ acidity function based on the protonation of 17 diphenylamines in 20 volume % ethanol-aqueous sulfuric acid has been established. The Hₒ value for the most acidic solution studied is -6.97 for 11.2 molar sulfuric acid. This acidity function differs from that based on the protonation of azobenzenes in the same solvent system; the latter acidity function diverges to more, negative Hₒ values as the sulfuric acid concentration increases. The pKBH+ values for the protonation of the diphenylamines vary from 1.36 for 4 methoxydiphenylamine to -6.21 for 4,4'-dinitrodiphenylamine. A plot, of log KBH+ versus Hammett ϭ constants for five mono-substituted diphenylamines yields a rho (ρ) value of.3.36. The pKBH+ values for 4-methoxy-, 4-methyl-, 4-methylsulfonyl-, and 4-nitro-diphenylamine are all less (morenegative) than expected from the Hammett substituent constants. Substituent effects on the basicities of aniline and diphenylamine are the same. This is evident from the fact, that a plot of the pKBH+ values of 11 diphenylamines versus the pKBH+ values of the corresponding anilines yields a good straight line with slope 1.01. The basicities of several nitro-substituted diphenylamines appear to vary regularly and do not reflect the presence of a strong interaction between the nitro group and sulfuric acid. A plot of the acidity versus the basicity (pKHA versus pKBH+) for nine diphenylamines yields, a straight line with slope 1.30. In a similar plot for 33 substituted anilines and diphenylamines two types of behaviour are observed. Those anilines and diphenylamines without an ortho or para hitro group fall about the line with slope 1.30 while those amines with at least one nitro group in the ortho or para position fall on a different, curved line with a slope of less than unity. / Science, Faculty of / Chemistry, Department of / Graduate

The altered acidities of amino acid residues in folded proteins can be used as a good indication for the diverse functions, stabilities as well as folding-unfolding states of the proteins. Previously, our group has investigated the gas phase acidities of a series of cysteine containing peptides of four residues and longer. The results showed that the helix macrodipole might have a significant influence on the acidities of these peptides. In this work, the gas phase acidities of isomeric small cysteine containing di- and tri-peptides were investigated experimentally and computationally. The gas phase acidities (ΔacidG) and related thermochemical quantities (ΔacidH and ΔacidS) were determined by using the extended Cooks kinetic method. A triple-quadruple mass spectrometer interfaced with an electrospray ionization source was employed for the study. The gas phase acidities of the N-terminal cysteine peptides (CysAla1,2NH2 and CysGly1,2NH2) were determined to be in the range of 321-323 kcal/mol, and the acidities of the C-terminal cysteine peptides (Ala1,2CysNH2 and Gly1,2CysNH2) were around 327- 331 kcal/mol. The results showed that theN-cysteine peptides were more acidic than the corresponding C-cysteine peptides, tri-peptides were stronger acids than di-peptides, and the acidities of cysteine-polyglycine peptides were close to those of the cysteine-polyalanine analogues. Computational studies were performed through conformer search, geometry optimization, and energy calculations using the Spartan and the Gaussian suite of programs. The results showed that the low energy conformations of all deprotonated peptides were coils. The greater acidities of the N-cysteine peptides were likely due to the stronger hydrogen-bonding interactions in the deprotonated N-cysteine peptides, which efficiently stabilized the thiolate anions. The theoretically predicted acidities were in good agreements with the experimental results.

Tobacco smoke particulate matter (PM) is a complex mixture of condensed organic compounds, with about 5 to 10% water. Its general properties are similar in some respects to that of atmospheric organic aerosol PM and thus provides a useful surrogate when studying atmospheric PM. Due to its ability to undergo acid-base chemistry, nicotine is of particular interest in the tobacco smoke system. The gas/particle partitioning of nicotine depends on the protonation state of nicotine in the particles, so the distribution of nicotine between these phases provides a means of understanding the acid-base balance in the tobacco smoke system. The goal of this work is to develop an acid-base balance for mainstream tobacco smoke that accounts for the extent of protonation of nicotine. Samples of extracted smoke particulate matter from seven brands of cigarettes were analyzed by ion chromatography (IC) and titration by both acid (HCl) and base (lithium phenoxide) for comparison with nicotine data collected by colleagues. IC analysis was used to quantify tracers of known acidic and basic species in tobacco smoke. Anion tracers for acids included: glycolate, acetate, formate, lactate, chloride, nitrite, sulfate, and nitrate. The cation tracers for base were ammonium, sodium, and potassium. The tobacco smoke extracts were also analyzed after acidification by the HCl titrant for changes in ammonia and organic acid concentrations to determine whether "bound" forms of these compounds were present in the PM. The titration data provided total concentrations of weak acid and bases in the samples. This titration data was compared with the concentrations of the tracers for weak acids and bases (along with the quantification of total nicotine by colleagues) to determine whether the IC analyses were accounting for all of the important species. The results of this comparison show that these analyses missed relevant species in the tobacco smoke system. As tobacco smoke PM is a complex organic mixture, the ability of acid species to protonate nicotine will be different than in aqueous media. The acidic species of interest were assumed to be either strong or weak, with the strong species assumed to be fully ionized after protonation of nicotine. Some portion of the weak acid species could then protonate any available nicotine. An electroneutrality equation (ENE) was developed for the tobacco smoke PM and populated using the IC data and the nicotine data obtained by colleagues. Using this ENE, the extent ionization of the weak acids species (α1A) and the net reaction constant for the protonation of nicotine by these weak acids (K*) was estimated. However, interpretation of the results were complicated by the underrepresentation of the pertinent weak acid species in our IC analyses. This study concluded that further work is needed to identify the missing weak acid and base species to obtain a better representation of the acid-base balance in tobacco smoke PM and to understand the ability of these weak acid species to protonate nicotine.

Akademisk avhandling--København. / Dansk resumé. Bibliography: p. [205]-228.

Akademisk avhandling--København. / Dansk resumé. Bibliography: p. [205]-228.

A Thesis submitted to The University of Arizona College of Medicine - Phoenix in partial fulfillment of the requirements for the Degree of Doctor of Medicine. / Previous studies suggest that dietary patterns that promote acidosis may have a negative effect on bone density, whereas a more alkaline‐based profile would be associated with better bone health. Thus, the aim of this study was to assess, in omnivores, vegetarians, and vegans bone mineral density using Dual‐energy X‐ray absorptiometry (DEXA) and compare it to their acid‐base status as indicated by urinary pH, Potential Renal Acid Load (PRAL) and serum anion gap. Our hypothesis was that plant‐based diets would be associated with a more alkaline acid‐base profile than omnivorous diets, and thus have a higher bone mineral density. Methods: We conducted a cross‐sectional study where we compared plant based vs. omnivorous diets. Eighty‐two subjects were enrolled in the study (27 omnivores, 27 vegetarians, and 28 vegans). Subjects were asked to fill out a medical history form and a 24‐ hour diet recall, and to complete a 24‐hour urine collection. After a few weeks, subjects returned to the test site to complete a DEXA scan. Acid base‐balance and bone health were determined using PRAL, urine pH, and anion gap as biomarkers for pH, and DEXA as an indicator of bone density. Our results showed that bone mineral density did not differ significantly between groups, although lacto‐ovo and vegan diets were more alkaline compared to meat based diets (6.5  0.4, 6.7  0.4, and 6.2  0.4 pH respectively, p = 0.003). Protein intake was found to be reduced by ~30% in individuals adhering to a lacto‐ovarian or vegan diet; yet protein was only associated with bone mineral density in those following vegan diets. Conversely, urinary pH was associated with bone mineral density only in those following a meat‐based diet. The significance of this study is that it provides knowledge in the area of osteoporosis prevention and perhaps specific recommendations based on diet groups: increased fruit and vegetable intake for those with high meat consumption, to improve the acid‐base homeostasis, and increased plant protein intake for individuals who follow a plant-based diet.

Orientador: Alessandro Moura Zagatto / Coorientador: Marcelo Papoti / Banca: Bruno Gualano / Banca: Bryan Saunders / Banca: Fúlvia de Barros Manchado Gobatto / Banca: Eduardo Zapaterra Campos / Resumo: O objetivo da presente tese foi verificar a influência da suplementação de β-Alanina associado ao treinamento intervalado de alta intensidade (HIIT) na performance de sprints repetidos. Participaram do estudo conduzido em caráter randomizado e duplo-cego, 20 jovens saudáveis alocados em dois grupos (Gβ [n = 10] - 6,4 g.dia-1 de β-Alanina; GP [n = 10] - 6,4 g.dia-1 de dextrose - placebo). Os participantes foram avaliados em três momentos distintos, previamente ao início, após quatro semanas de HIIT sem suplementação e após 6 semanas de suplementação + HIIT. As avaliações foram compostas por teste incremental até exaustão (TINC); séries de 12 sprints repetidos (RSA); e teste de tempo limite até exaustão a 115% da velocidade máxima atingida no TINC (TLIM). Previamente e imediatamente após TINC e RSA foram realizadas avaliações neuromusculares compostas por saltos verticais máximos, contrações isométricas máximas de extensão de joelho e estimulação elétrica periférica. O HIIT foi composto de dez corridas de 1 min a 90% da velocidade máxima atingida no TINC, com 1 min de recuperação passiva entre as corridas e frequência de 3 sessões semanais. Previamente ao início da suplementação + HIIT e ao final da intervenção, os participantes foram submetidos a biópsias musculares para determinação do conteúdo de carnosina intramuscular, capacidade de tamponamento in vitro e conteúdo de proteínas/enzimas chaves. Após a intervenção, ambos os grupos melhoraram o metabolismo oxidativo (i.e., co... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of the present thesis was to verify the influence of β-Alanine supplementation associated with high intensity interval training (HIIT) on the performance of repeated sprints. The study was conducted in a randomized, double-blind design and 20 healthy young men were allocated in two groups (Gβ [n = 10] - 6.4 g.day-1 of β-Alanine; GP [n = 10] - 6.4 g.day-1 of dextrose - placebo). The participants were evaluated at three different moments, prior to beginning, after four weeks of HIIT without supplementation and after 6 weeks of supplementation + HIIT. The evaluations were composed by incremental test until exhaustion (TINC); set of 12 repeated sprints (RSA); and time-to-exhaustion test at 115% of the maximum velocity achieved in TINC (TLIM). Previously and immediately after TINC and RSA, neuromuscular evaluations were performed, consisting of maximum vertical jumps, maximal voluntary isometric contractions of knee extension and peripheral electrical stimulation. The HIIT was composed by ten runs of 1-min at 90% of the maximum velocity achieved in TINC, with 1-min of passive recovery between runs and frequency of 3 sessions per week. Prior to the initiation of supplementation + HIIT and at the end of the intervention, the participants underwent muscle biopsies to determine intramuscular carnosine content, muscle buffer capacity in vitro and key protein/enzyme content. After the intervention, both groups improved oxidative metabolism (i.e., maximal oxygen uptake), however, only Gβ significantly improved the intramuscular carnosine content and the RSA variables; in addition to presenting attenuation of the neuromuscular fatigue induced by the RSA. No significant differences were observed in anaerobic capacity, muscle buffer capacity in vitro and key protein/enzyme content. Thus, the association between β-Alanine supplementation and HIIT provided significant improvement in repeated sprints performan / Doutor

I investigated cellular mechanisms of ion and acid-base transport in rainbow trout (Oncorhyncus mykiss), crabs (Neohelice granulata), zebrafish (Danio rerio), Pacific hagfish (Eptatretus stoutii), and mosquito larvae (Aedes aegypti) with a primary focus on discerning the mechanisms governing ion transport and acid base regulation. In rainbow trout I provide the first functional evidence for two physiologically distinct mitochondrion-rich (MR) cells at the gill and demonstrate a new model for transepithelial Na+ uptake from freshwater involving apical Na+ channels and basolateral Na+/HCO3- co-transporters. These data are supported by extensive thermodynamic consideration of Na+ uptake from freshwater. I also demonstrate functional Cl-/HCO3- exchangers in both MR cell subtypes with roles for Cl- uptake and intracellular pH (pHi) regulation respectively and I present the first evidence for a Cl- dependent Na+/H+ exchanger in gill MR cells. Finally I demonstrate a unique Na+ dependent pHi recovery mechanism that requires protein kinase C for activation. A major limiting factor in clarifying the mechanisms of Na+ uptake in freshwater fish is the lack of a typical Na+ channel in any of the fish molecular databases. My work on zebrafish, although preliminary, indicates that a member of the acid-sensing ion channel family could be responsible for Na+ uptake from freshwater. I then expanded my research outside the trout model using an isolated crab gill preparation. I provide a cellular model for H+ secretion in crab gills that supports the transepithelial Na+ transport model that I described in rainbow trout. In Pacific hagfish, I demonstrate that recovery from blood acidosis is dependent on a Na+/H+ exchanger in gill MR cells. This mechanism of regulation involves translocation from the cytoplasm to the apical membrane during acidotic stress. This data combines with other studies demonstrating the mechanisms of acid and base secretion from a single MR cell subtype. Finally, I show that serotonin stimulation alkalinizes the pHi of the anterior midgut cells in the larval mosquito to levels never before observed in cell biology. These data challenge the dogma of pHi regulation in cell biology and demonstrate the power of using a comparative approach to systems physiology. / Physiology, Cell and Developmental Biology