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Thesis (Ph. D.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2004. / Includes bibliographical references.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

No description available.

No description available.

Le diabète est associé à divers types de complications au niveau vasculaire affectant la micro et la macro-vasculature, ce qui contribue à l'augmentation de l'incidence d'infarctus du myocarde, d'ACV, de néphropathie et de rétinopathie. Parmi les mécanismes expliquant l'apparition de ces complications, la glycation des protéines joue un rôle important. En effet, il est connu que la glycation des protéines de la matrice extracellulaire (élastine, collagène) affecte les propriétés mécaniques des tissus constitués de celles-ci. Nous pensons que la glycation des protéines du cytosquelette peut également affecter les propriétés mécaniques de cellules présentes au niveau de la vasculature, telles que la cellule du muscle lisse vasculaire ou la cellule endothéliale, et ainsi affecter les fonctions cellulaires dépendantes d'une réorganisation du cytosquelette, telles que la contraction cellulaire. Le glyoxal (GO) est un composé hautement réactif de la famille des oxoaldéhydes, considéré comme un puissant agent de glycation au niveau cellulaire, puisqu'il réagit rapidement avec les groupements amines des protéines de façon à former des produits de glycation avancés (PGA). L'étude présentée dans cette thèse démontre d'une part que l'exposition à cet agent de glycation entraîne une augmentation de la rigidité cellulaire ainsi qu'une augmentation de la réponse contractile cellulaire générée par la machinerie actomyosine, en réponse à l'AngII. À la lumière de ces résultats, nous proposons qu'une exposition au GO peut induire des modifications post-traductionnelles de type non-enzymatique des protéines impliquées dans la machinerie contractile et ainsi altérer la fonction contractile cellulaire. C'est pourquoi nous avons en second lieu évalué la glycation de trois protéines impliquées dans la machinerie contractile (actine, ROCK, gelsoline) par un essai basé sur la réaction d'une sonde fluorescente et perméable à la membrane cellulaire, soit le carboxyfluorescéine diacetate succinimidyl ester (CFDA-SE), avec les amines primaires des protéines. Par cet essai, nous avons observé une augmentation de la glycation de l'actine et de ROCK, de même qu'une augmentation de l'interaction entre l'actine et la GSN. Cette thèse montre également l'implication de l'activité kinase de ROCK dans l'amplification de la réponse contractile, suggérant que la glycation de ROCK pourrait moduler son activité. En conclusion, la modification des protéines cellulaires par le GO pourrait affecter leurs fonctions et propriétés mécaniques, notamment par la modulation d'importantes interactions protéine-protéine impliquées dans la contraction cellulaire et dans l'organisation du cytosquelette.

Doctor of Philosophy / Food Science Institute / J. Scott Smith / Advanced glycation endproducts (AGEs) are formed in many cooked meat products via Maillard browning reactions. Current research suggests consumption of these compounds may be a contributor to chronic diseases such as diabetes and heart diseases. Thus, information on the prevalence and inhibition of these compounds in food is desirable. The first objective was to determine the AGE content, as determined as N[superscript]ε-carboxymethyllysine (CML) level, in cooked meat and fish prepared by general cooking methods recommended by U.S. Department of Agriculture, Food Safety and Inspection Service (USDA-FSIS). We found AGE was detected in all the cooked samples, but the levels depended on the different cooking conditions. Broiling and frying at higher cooking temperatures produced higher levels of CML and broiled beef contained the highest CML content (21.84 μg/g). However, the baked salmon (8.59 μg/g) and baked tilapia (9.72 μg/g) contained less CML as compared to the other samples. In order to investigate the inhibitory effect of selected natural antioxidant on AGEs formation in cooked meat, four cereal brans, wheat (Jagger, JA), triticale (Spring Triticale, ST; Thundercale, TH), and Rye (RY) bran were added to beef patties before cooking. RY (42.0% inhibition), ST (27.5% inhibition), and TH (21.4% inhibition) brans significantly decreased CML formation compared with the control. The inhibition of CML was correlated to the water-holding activity (WHC) of the samples, and the radical scavenging activity of the brans. The effect of cereal bran extracts (JA, ST, TH, and RY), was studied in a bovine serum albumin and glucose (BSA-GLU) model system. The ST extract significantly (P <0.05) inhibited CML formation compared to the control group. ST particularly contained vanillic acid (VA), chlorogenic acid (CHA), gentisic acid (GEA), and ferulic acid (FA), where GEA and CHA mitigated CML with an average percentage decrease of 29.6% for CHA and 51.1% for GEA. It therefore may be useful in preventing AGEs formation by using ST bran as a food addictive, which contains abundant phenolic acids. In summary, current dietary AGEs database will provide important information for use in estimating AGEs exposure, and also these data demonstrate that a significantly reduced intake of dietary AGEs can be achieved by low heat AGE cooking methods such as baking, which can be used at home or in the meat industry. Cereal bran addition to meat products may reduce formation of AGEs that is a desired attribute for the processed meat products industry.

Glycoproteins have diverse and essential roles within biological systems. They are formed by enzymatic addition of saccharides to proteins during, or shortly after, translation. However, saccharides can also react with proteins non-enzymatically, a process termed glycation, which can cause impaired function and improper folding. Glycated proteins further react to form advanced glycation end-products, which have been implicated in the pathogenesis and progress of many diseases. Due to this pathological effect, glycation has been studied as a potential biomarker of these diseases. Photoaffinity labelling is a technique that is used to investigate the structure, and presence, of biological molecules; a precedent exists for its use in the study of carbohydrates in biological systems. Chapter 1 outlines the background of this thesis exploring previous studies of glycation, its effects, and methods used in recognition and photoaffinity labelling. Chapter 2 details the design and synthesis of a novel photoaffinity probe, and the optimisation of this synthesis. The target molecule was successfully produced and simpler alternatives to the initial synthetic route with similar yields are discussed. In Chapter 3 the use of the photoaffinity probe is studied. Labelling trials were performed on three proteins: human serum albumin (HSA), macrophage migration inhibitory factor (MIF), and casein. Mass spectrometry showed that the experiments with both HSA and MIF were successful, while the procedure appeared to lead to degradation of casein. Additionally, our work into developing techniques for identifying labelled samples is detailed. A diol-doped electrophoresis gel was not successful created, however, staining protein samples in polyacrylamide gel electrophoresis with curcumin showed promise. Chapter 4 explores the electrochemistry of the photoaffinity probe and details the use of the probe in functionalising a fluorine doped tin oxide (FTO) glass electrode. Cyclic voltammograms of Alizarin Red S (ARS), obtained using a treated electrode, suggest that surface functionalisation was successful.