This work was undertaken to evaluate interactions between plant proteins and selected volatile flavour compounds on flavour delivery and heat-induced gelation properties for canola, pea and wheat proteins. An automated dynamic headspace GC/MS approach was adopted to monitor the change in flavour intensity in aqueous model systems. The extent of flavour binding was a function of protein source, protein isolation method and stereochemistry of the flavour compound. Using Differential Scanning Calorimetry and intrinsic fluorimetry, potential conformational changes due to partial denaturation of proteins were observed. Aldehyde flavours exhibited much higher “unfolding capacity” than ketones, which accounted for their remarkable binding affinities. Two volatile flavour by-products, 2-butyl-2-octenal and 2-pentyl-2-nonenal, were detected from the interactions between salt-extracted canola protein isolates (CPIs) with hexanal and heptanal, respectively, due to aldolisation reactions. Competitive bindings among homologous ketones and between heterologous aldehyde and ketone mixture were observed, while a synergistic effect was noted for aldehyde flavour mixtures. Environmental changes such as heating and addition of non-chaotropic salts increased binding for ketones; however, protein aggregation following continuous heating and denaturation of protein by chaotropic salt and at extreme pH values reduced ketone retention. Apart from molecular interactions, dramatic increases in flavour binding were monitored when physical adsorption of flavours on aggregated proteins was employed. By adding bonding disrupting agents, the molecular forces responsible for the interactions were probed with hydrophobic interactions, hydrogen bond and ionic interactions being prominent for benzaldehyde, 2-octanone and hexyl acetate, whereas covalent interactions were implicated for octanal and dibutyl disulfide. Selectively modifying proteins via chemical (acetylation and succinylation) and enzymatic (Alcalase) approaches significantly altered protein-flavour binding affinities and this was influenced by the type of flavours selected and associated type of binding. In general, addition of flavour compounds diminished protein heat-induced gel forming properties by disrupting protein inter- and intra-molecular hydrophobic interactions. However, gel strength was regained with increasing concentration and chain length of aldehydes possibly due to the additional unfolding effect on proteins due to aldehyde binding. This facilitated the gel formation process, consequently resulting in formation of stronger gels. / February 2016

Durant ce travail de thèse, nous nous sommes intéressés au comportement hydromécanique d’un éco-géo-matériau à base de terre crue. Différents aspects ont été traités visant l’optimisation de sa formulation et aussi ses interactions avec les renforts. Nous avons tenté de lever trois verrous scientifiques : l’optimisation des interactions physico-chimiques argiles-liants, l’identification des mécanismes de fissuration en relation avec la succion, et les interactions électrochimiques sol-armatures en acier. L’ajout de la chaux impose le comportement du sol à court terme et favorise le gain en résistance en rendant le milieu plus alcalin. Nous avons montré qu’à l’aide d’une mesure macroscopique, la conductivité électrique, nous pouvons suivre les interactions sol-liants. Lors de la dessiccation d’un sol argileux, le retrait global est homogène. Une déformation locale hétérogène induit des contraintes de traction responsables de l’apparition des fissures. L’ajout des renforts réduit le pourcentage de fissuration d’un facteur 10. La succion générée lors du séchage est interprétée en termes de contraintes de traction. Le contact entre la terre et l’acier entraine des réactions d’oxydoréduction dont le produit est la corrosion. Trois familles d’argiles ont été testées. La vitesse de corrosion obtenue est de l’ordre de 3μm/an. / Throughout this thesis, we are interested in hydro-mechanical behavior of an eco-geo-material based on raw earth. Different aspects have been treated viewing the optimization of his formulation as well as its interactions with the reinforcements. We have tried to resolve the following three scientific locks: the optimization of the physical-chemical clay-binders’ interactions, the identification of the mechanisms of cracking in relation with the suction and the electrochemical soil-iron interactions. Adding lime imposes the behavior of the soil and improves its resistance by making the environment more alkaline. We showed that we can follow soil-binders’ interactions by using the electrical conductivity technique. During desiccation of a clayey soil, global shrinkage is homogenous. A heterogonous local deformation induces tensile stress responsible of cracking. Adding reinforcement reduces crack ratio by a factor 10. Suction generated during drying is interpreted in terms of tensile stresses. Interaction between earth and metal allows oxydo-reduction reactions producing corrosion. Three type of clay were tested. Corrosion speed is about 3μm/year.

<p> According to the World Health Organization, long-term exposures to heavy metal toxicants such as arsenic (As) and lead (Pb), even at the parts per billion (ppb, μg/L) level, can cause severe health problems such as cancer, skin lesions, and cardiovascular diseases. Therefore, an accurate and rapid heavy metal toxicant monitoring technique is needed. This research investigated the proof-of-the concept of a portable sensor for detecting As and Pb in water. The sensor system utilized a Quartz Crystal Microbalance - QCM (openQCM w-i2) system interfaced with a computer as the sensing platform. It was further integrated with a peristaltic pump and required tubing to create the integrated sensing system. It used a 10 MHz AT-cut quartz crystal gold electrode as the sensing substrate. For the determination of As in water, dithiothreitol (DTT) was used as the ligand to be deposited on the gold electrode using the Self-assembly-monolayer method (SAM). For the determination of Pb, a combination of ligands (Chitosan, Glutaraldehyde, and lead ionophore II - CGL) was used and deposited on the gold electrode using the spin-coating method. The system was tested for As in water with specific concentrations (0, 50, 100, and 200 ppb) under laboratory conditions. Similarly, the system was tested for Pb in water with different concentrations (0, 10, 25, 50, and 100 ppb) under laboratory conditions. The resulted change of frequency (with respect to time, in seconds) of the QCM system to different concentrations of the individual analyte was recorded. Subsequently, the recorded data were analyzed to determine the correlation model and coefficient of determination, R2. The maximum R2 values for detecting As and Pb were 0.963 and 0.991, respectively. Thus, this proof-of-the-concept study using the developed QCM-based sensing system for detecting As and Pb in water was successful.</p>

Macromolecular interactions play very important roles in regulation of all levels of biological processes. Aberrant macromolecular interactions often result in diseases. By applying a combination of spectroscopy, calorimetry, computation and other techniques, the protein-protein interactions in the system of the Shaw2 Kv channel and the protein-RNA interactions in West Nile virus RNA-cellular protein TIAR complex were explored. In the former system, the results shed light on the local structures of the key channel components and their potential interaction mediated by butanol, a general anesthetic. In the later studies, the binding modes of TIAR RRM2 to oligoU RNAs and West Nile virus RNAs were investigated. These findings provided insights into the basis of the specific cellular protein–viral RNA interaction and preliminary data for the development of strategies on how to interfere with virus replication