Myoglobin (Mb) is a well characterized hemeprotein found in skeletal muscle. The dimethylester heme-substituted derivative of equine Mb (DME-Mb) was prepared to evaluate the involvement of the heme propionate groups in the electron transfer reactions of Mb. To achieve this goal, an efficient procedure to reconstitute and purify DME-Mb in high yield was developed. The near UV-visible absorption spectra of DME-Mb in various states of ligation and oxidation did not change significantly relative to those of native Mb. The ¹H NMR spectra obtained for native metMb (heme Fe(III) oxidation state) and metDME-Mb showed differences in the electromagnetic environment of their respective heme groups. The reactivity of DME-Mb was different from that of native Mb. For example the water ligand of metDME-Mb (Fe-H₂O) has a lower pKa than that of native metMb as determined by spectroscopic pH titrations. The autoxidation rate of oxyDME-Mb (Fe(II)-O₂) is faster than that of native oxyMb. MetDME-Mb apparently has a binding affinity for ferricyanide not evident in native metMb. Compared to native Mb, DME-Mb has decreased susceptibility to the oxidant hydrogen peroxide. The oxidation-reduction equilibrium of DME-Mb has been studied under a variety of solution conditions. At standard conditions (pH 7, I=0.1 M and 25°C) the midpoint reduction potential (Em) of DME-Mb is 100.0(2) mV vs. SHE, which is 39 mV higher than the Em of native Mb. Analysis of the pH dependence of Em showed differences in the identity or pKa between titratable groups found in native and DME-Mb. The ionic strength dependence of Em showed a higher net positive charge estimate for DME-Mb than native Mb consistent with the nature of the chemical modification involved. The temperature dependence of Em showed that DME-Mb has a greater difference in stability between oxidation states than native Mb. The kinetics of metDME-Mb reduction by Fe(EDTA)²⁻were also studied under a variety of conditions. At standard conditions, metDME-Mb reacted with the reductant Fe(EDTA)²⁻ at a second order rate constant (k₁₂) two orders of magnitude greater than that of native metMb. After correcting for the differences in reduction potential between reactants, metDME-Mb still reacted at a significantly faster rate than native metMb, indicating differences in their reaction mechanisms. The pH, temperature and ionic strength dependences of k₁₂ for DME-Mb and Fe(EDTA)²⁻ showed that DME-Mb had electrostatic and thermodynamic properties significantly different from that of native Mb. The functional differences between DME-Mb and native Mb can be attributed to the structural and electrostatics properties of the heme propionate groups. The interactions of these groups within the surrounding protein and the external environment are discussed with reference to the structure of Mb available from x-ray crystallographic studies. As a result, it is concluded that the heme propionate groups are involved in the structural stability, electron transfer specificity and reactivity of Mb. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains x, 88 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Les solutions électro-activées (SEA) obtenues par excitation électrique de solutions aqueuses sont actuellement étudiées par leur haut potentiel de préservation des aliments en raison de leurs propriétés antimicrobiennes et sporicides. Ainsi, ce projet visait à électro-activer des solutions aqueuses de citrate (CS), de propionate (PS) et d’acétate de sodium (AS) pour les utiliser comme saumures dans un procédé de conservation de betterave rouge (BR). Dans ce projet, le taux d’acidité titrable (% AT), le pH et le potentiel oxydo-réduction (POR) des SEA générées ont été étudiées en fonction de la concentration du sel, de l’intensité de courant électrique (IC) appliquée et du temps de traitement qui s’est étalé sur une période de 75 minutes. Ensuite, trois SEA de chaque type de sel ont été sélectionnées selon le % d’AT : minimal (≈0,8), moyen (≈1,3) et maximale (≈1,5) et utilisées tant pour blanchir des morceaux de BR à 90 °C pendant 3 min comme que pour la mise en conserve du produit. La qualité microbiologique, chromatique et texturale a été évaluée en fonction du type de SEA utilisé pour la conservation du produit pendant un mois. Les résultats obtenus montrent que l’IC est le facteur qui influence significativement les propriétés des SEA. Des valeurs de pH de 1,5 à 4, de POR d’environ +500 mV pour le citrate et +1200 mV pour le propionate et l'acétate, et un % d’AT de 0,8 à 2 mmole/L (1.5 pour l’acétate de sodium) ont été obtenues. Les SEA de citrate de sodium et de propionate de sodium ont montré une très bonne activité antimicrobienne même à 0,8 % d’AT, tandis que pour l’acétate de sodium, cette activité était observée à 1,5% d’AT. La couleur est devenue plus pâle avec le temps de conservation et la force de mastication a été en général peu affectée. / Electro-activated solutions (EAS) obtained by electrical excitation of aqueous solutions are currently being studied for their high food preservation potential due to their antimicrobial and sporicidal properties. Thus, this project was aimed to electroactivate aqueous solutions of sodium citrate (CS), sodium propionate (PS) and sodium acetate (AS) to use them as brines in a conservation process of beetroot (BR). In this project, the electro-activated solutions titratable acidity (% TA), the pH and the oxidation-reduction potential (ORP) of the generated EAS were studied as a function of the salt concentration which was set for a total period of 75 minutes. Then, three EAS of each type of the used salts of organic acids were selected according to their % of TA: minimum (≈0.8), medium (≈1.3) and maximum (≈1.5), and were used in combination with a blanching process at temperature of 90 ° C for 3 min as a process for beetroot canning. The microbiological, chromatic and textural quality of the canned product was evaluated according to the type of ESA used for the preservation of the product during one month at ambient temperature (23 ± 1 °C). The results obtained showed that the CI is the factor which significantly (p < 0.001) influenced the properties of the ESA. The pH values of 1.5 to 4, ORP of around +500 mV for the electro-activated (EA) sodium citrate solution and +1200 mV for the EA sodium propionate and sodium acetate solutions, and %AT of 0.8 to 2 mmole/L (1.5 for EA sodium acetate solution) were obtained. The EAS of sodium citrate and sodium propionate showed very good antimicrobial activity even at 0.8% of TA, while for the EA sodium acetate solution, this activity was observed at 1.5% TA. The color of the canned beetroot became lighter over time and the corresponding chewing force calculated by textural profile analysis (TPA) analysis was generally slightly affected by the used preservation procedure.

Photocopy of typescript. / Digitized by Kansas Correctional Industries

A variety of heterocyclic alcohols were coupled with silyl ketene acetals and other [pi]-nucleophiles in the presence of trimethylsilyl trifluoromethanesulfonate to provide an array of substituted [beta]-heteroaryl propionates, including those with contiguous quaternary centers. This reaction also proceeds with high diastereoselectivity when the [pi]-nucleophile bears a chiral auxiliary. The formal synthesis of N-methylwelwitindolinone C isothiocyanate, a densely functionalized alkaloid with the ability to reverse multiple drug resistance, was completed featuring several key transformations. The first key transformation consisted of coupling a heterocyclic alcohol with a silyl ketene acetal to give a highly functionalized intermediate. Next, a palladium catalyzed enolate arylation followed by an intramolecular allylic alkylation successfully constructed the bicyclo(4.3.1)decane backbone of the N-methylwelwitindolinone C isothiocyanate. / text

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

No description available.