Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [214]-226).

Thesis (Ph. D.)--University of Massachusetts Amherst, 2009. / Includes bibliographical references (p. 98-107). Print copy also available.

The characteristics of transport by the epithelial, proton-coupled oligopeptide transporter, PepT1, have been investigated in PepT1 expressing Xenopus laevis oocytes using electrophysiological techniques. Membrane depolarisations and inward currents have been measured in response to various dipeptide substrates, including structurally modified and charged peptides. The latter part of this study has focussed on the role of phorbol esters on the regulation of PepT1-mediated peptide transport. I have shown that transport of neutral peptides is dependent on both pH and membrane potential. In addition, the carboxyl terminus plays an important role in substrate recognition and binding, as when blocked, the affinity of the substrate is reduced 10-fold. The importance of position of charge within a dipeptide on substrate binding has also been investigated using dipeptides where the charged amino acid residue is present at either the amino or carboxyl terminus. The results showed that the apparent order of affinity reversed upon extracellular acidification, thus charged residues within the peptide play an important role in substrate binding. The acute regulation of the oligopeptide transporter has been examined by studying the effects of phorbol esters on the transport of a neutral peptide, Gly-Gln. The active ester, PMA, was shown to decrease both the K_a and the I_max. Immunocytochemical studies have confirmed the electrophysiological findings.

Thesis (Ph.D.) - University of St Andrews, August 2008.

The thesis consists of three essays. In the first essay, the strategic effects of bonus/penalty compensation contracts are analysed. This essay consists of the first three chapters of the thesis. In Chapter 1, viewing each firm as a "principal-agent" pair, we examine firms' rivalry in bonus/penalty contracts in oligopolistic markets when the agents are risk-neutral. Under standard assumptions concerning production, demand, and cost functions, we show that bonus/penalty contracts may be used for strategic purposes. We find that whether agents' actions would (in equilibrium) be encouraged through bonuses or discouraged through penalties would critically depend on the existing strategic relationships between agents' actions or firms' products. We further show that firms' capita] stocks can affect their strategic positions in the bonus/penalty rivalry. The social welfare implication of the bonus/penalty rivalry is also examined. In Chapter 2, using a general framework of rivalrous agency with risk-averse agents, we identify two distinctive effects of bonus/penalty contracting, namely, the strategic effect and the incentive effect. We find that the two effects may or may not work in the same direction for a principal-agent pair, depending on the nature of strategic relationships between agents' actions. In Chapter 3, we compare the strategic effects of bonus/penalty contracts with that of linear contracts. We find that, if only one principal is active in designing agency compensation contracts, then he/she would be indifferent between a bonus/penalty contract and a linear contract. If both principals are active in designing agency contracts, however, the choice between bonus/penalty and linear contracts would in general matter to the principals. In particular, we show in an example that both principals would non-cooperatively choose a bonus contract over a linear contract. The second essay of the thesis, as in Chapter 4, presents an analysis of common sales agents based on their precommitment role when consumers are imperfectly informed about the products on the market. We show that an exclusive channel stucture can create a cost due to exclusive channels' inability to commit themselves to sales impartiality. We further show that independent non-cooperative firms may use common agents as a precommitment device to convince potential consumers that the risk of being misrepresented has been reduced or eliminated. We demonstrate that a market involving common sales agents can arise as an equilibrium outcome. Our analysis shows that common sales agents can be welfare improving for both firms and consumers. The third essay, as in Chapter 5, investigates the dynamic pattern of firm competitive conduct, using time-series and firm-specific data for a set of duopoly airline routes. We estimate the mean conduct parameters for each firm and each period, and infer whether the data are consistent with the Cournot, Bertrand, Friedman, or Green-Porter models. We find that airlines' competitive behavior may switch between the competitive and collusive regimes. Moreover, we find that airline profits in a collusive period appear less than the (single-period) monopoly profits, and the degree of overall market competitiveness is between the Cournot and monopoly solutions but closer to the Cournot solution. Our data suggest that major carriers might use quantity volumes, rather than prices, as their strategy variables. We also conduct some Bayesian analysis of seeing how our results would influence priors associated with different models. We illustrate a model choice criterion based on Bayesian analysis and use the criterion to choose the "best" model among competing models. / Business, Sauder School 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.

No description available.

La prise de conscience que les qualités nutritionnelles des protéines allaient au-delà de leur capacité à fournir des acides aminés, est apparue avec l'émergence de la notion de peptides bioactifs, c'est-à-dire d'oligopeptides principalement produits par protéolyse, pouvant être des modulateurs de divers processus biologiques. Si de nombreux peptides bioactifs ont été découverts dans des hydrolysats de protéines de lait, leur recherche dans les produits carnés reste à ce jour très peu développée. Dans ce contexte, nos objectifs ont été de caractériser et d'identifier les peptides (< 5 kDa) présents dans la chair de poisson ou viande bovine après conservation/maturation et cuisson, puis au cours de l'hydrolyse digestive in vivo chez le porc dans les contenus intestinaux et dans le sang portal. La fraction peptidique des aliments, constituée des peptides non protéiniques (carnosine, ansérine, glutathion) et de ceux formés au cours des traitements technologiques (conservation et cuisson), était dépendante de l'espèce et des traitements appliqués. Dans la viande bovine cuite, où de nombreux peptides ont été détectés, des fragments de protéines de structure ont été identifiés. Parmi la grande diversité des peptides d'origine alimentaire trouvés dans les contenus duodénaux et jéjunaux, certains d'entre eux, présents de façon systématique, étaient de possibles peptides bioactifs ou leurs précurseurs. Outre la carnosine dont la biodisponibilité dépendait d'abord de sa teneur dans la viande, de nombreux composés, probablement des oligopeptides, étaient libérés dans le sang de la veine porte selon des profils spécifiques après un repas de faux-filet ou de paleron.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

Thesis (Ph.D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on March 12, 2009) Includes bibliographical references.