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I. The function of aldehyde in the bacterial luminescent reaction was investigated using {1-('14)C} decanol in a coupled enzyme system. The substrates for the bioluminescent reaction, {1-('14)C} decanal and FMNH(,2), were generated in the reaction mixture by horse liver dehydrogenase and bacterial FMN reductase. Analysis of the reaction products indicated that aldehyde is exclusively convertted to the corresponding acid by bacterial luciferase. A linear relationship between light emission and acid production was obtained with a resulting quantum yield of 0.10 quanta per molecule of acid produced. / II. In order to determine if the lag period in luminescence observed during early exponential growth of Beneckea harveyi reflects the repression of synthesis of one or both subunits of luciferase at the level of gene transcription/translation or the synthesis of one or both polypeptide(s) in the form of an inactive precursor, a double labelling experiment was performed such that, the proteins synthesized during the luminescence lag and inductions periods were labelled with ('3)H-leucine and ('14)C-leucine respectively. Analysis of the radioactivity incorporated into the (alpha) and (beta) subunits of luciferase indicates that both subunits are coordinately controlled and that the induction of luminescence is reflected by preferential de-novo synthesis of luciferase during the induction period. Analysis of the soluble protein indicates that five additional polypeptides are co-induced with luciferase and that one polypeptide appears to be repressed during the induction period. Analysis of the radioactivity incorporated into NAD(P)H:flavin oxidoreductase (the major NADH dependent FMN reductase and a supplier of FMNH(,2) for the luminescent reaction) in Beneckea harveyi indicates that its synthesis is constitutive. / III. NAD(P)H:flavin oxidoreductase has been purified with the aid of affinity chromatography of (epsilon)-amino hexanoyl-FMN-Sepharose. The enzyme is composed of a single polypeptide chain of 24,000 daltons. Kinetic studies indicate that the higher specificity of the enzyme for NADH, riboflavin and FMN as opposed to NADPH and FAD is due primarily to variations in the Michaelis constants for the different substrates. Initial velocity studies with all pairs of substrates gave intersecting patterns supporting a sequential mechanism for the NAD(P)H:flavin oxidoreductase.

Carbon nanotubes (CNTs) have become some of the most promising drug delivery systems due to their unique properties, especially their high surface area and their ease to penetrate cells. The aim of this thesis was to render single walled carbon nanotubes (SWNTs) more biocompatible, and to test their ability to selectively deliver suitable dosages of anti-cancer drugs to αvβ3 integrins and epidermal growth factor receptor (EGFR) expressing cancer cells used as delivery targets. Those two targets are important to consider, as they are highly present on the cell membrane of several cancer cells, such as colon, breast, leukemic, and lung cancer. Results reveal that the combination of covalent and noncovalent surface modification of SWNTs increased SWNTs biocompatibility towards RAW 264.7 and Caco-2 cells by 17.4% and 20.8%, respectively, compared to covalently modified SWNTs. Results also show that the delivery of the widely used anti-cancer drug, doxorubicin (DOX), was higher when targeted by the SWNTs. In fact, the concentration of targeted DOX was 1.4 (± 0.3) folds higher and 2 (± 0.7) folds higher than that of free DOX in Caco-2 and RAW 264.7 cells, respectively. Similarly, the cytotoxicity of the SWNT-targeted DOX on RAW 264.7 cells at 48h post exposure was 3.6 folds higher than that of free DOX. Thus, the study reveals that SWNTs are capable to enhance drug effect on cancer cell lines. Further in vivo studies are recommended to evaluate the full potentials. / Grace à leurs propriétés uniques tel que leur grande surface de contact et leur aisance de pénètre les cellules humaines, les nanotubes de carbone sont désormais de prometteurs systèmes de livraison des médicaments. Le but de cette thèse est de rendre les nanotubes de carbone plus biocompatible, et de tester leur habileté de cibler la chimiothérapie vers les cellules cancéreuses qui possèdent les intégrines αvβ3 et les récepteurs EGF. Ces deux récepteurs sont spécifiquement ciblés car ils sont présents en grandes concentrations sur la surface des cellules cancéreuses telles que les cellules colorectales et les cellules du cancer du sein. Les résultats montrent que la modification covalente et non covalente de la surface des nanotubes de carbone augmente leur compatibilité envers les cellules RAW 264.7 et Caco-2 de 17% et 20.8%, respectivement, comparèrent aux nanotubes modifies de façon covalente seulement. Les résultats montrent aussi que la concentration de la chimiothérapie doxorubicine (DOX) était plus grande lorsqu'elle est délivrée par les nanotubes. En effet, la concentration de DOX délivrée par les nanotubes était 1.4 (± 0.3) et 2 (±0.4) fois plus élevée dans les cellules Caco-2 et RAW 264.7, respectivement, que celle de DOX délivrée sans système de livraison. De même, la cyto-toxicité de DOX délivré par les nanotubes de carbone aux cellules RAW 264.7 était 3.6 (± 0.7) fois plus élevée que celle de DOX délivrée sans système de livraison à 48 h post exposition. L'étude montre que les nanotubes de carbone sont capables d'augmenter la concentration du médicament dans les cellules cancéreuses. Pour étudier tout le potentiel des nanotubes de carbone, d'autres études in vivo seront nécessaire.

Retrotransposition is an active process in mammalian gene evolution. It involves the reverse transcription of an mRNA transcript and the subsequent re-integration of the resulting cDNA into genomic DNA. This study was to derive a complete picture of the role of gene retrotransposition in the genome evolution of vertebrates, particularly in mammals. A robust procedure to annotate putative retrogenes (PRs) was applied to eight vertebrate genomes (human, chimp, dog, cow, rat, mouse, chicken and the puffer-fish T. nigriviridis). Mammalian genomes were estimated to contain 400-800 PRs (up to ~4% of genes). For the eight genomes studied here, no significant correlation between the number of genes in a genome and the number of PRs established. Most of PRs (human and mouse) passed the gene order test thus the possibility that they arose from local or segmental duplication is precluded. Focusing on human and mouse, a few analyses were performed to investigate these PRs further. More than 200 genome-specific PRs were identified in mouse and rat, compared to ~40 in each of the primates human and chimp, indicating that in rodents there is more recent gene retrotransposition activity. Ka/Ks distribution for human PRs is similar to that for human retropseudogenes. However, some of mouse PRs may be under purifying selection, as supported by the fact that there is significant excess of mouse PRs with Ka/Ks < 0.5 compared to mouse retropseudogenes. / La rétrotransposition est un processus actif de l'évolution génétique des mammifères. Il implique la transcription inverse d'un transcrit d'ARNm et la subséquente réintégration de la résultante ADNc dans l'ADN génomique. Cette étude a pour objectif de trouver le portrait complet du rôle du gène de rétrotransposition dans l'évolution du génome des vertébrés, particulièrement les mammifères. Une procédure robuste afin d'annoter les rétrogènes putatifs (PRs) fut appliquée à huit génomes de vertébrés (humain, chimp, chien, vache, rat, souris, poule et le poisson-globe T. nigriviridis). Les génomes mammifériens furent estimés à contenir de 400 à 800 PRs (jusqu'à ~4% de gènes). Concernant les huit génomes étudiés dans ce cas-ci, aucune corrélation significative entre le nombre de gènes dans le génome et le nombre de PRs fut établit. La majorité des PRs (humain et souris) ont passé le test d'ordre génique, par conséquent la possibilité qu'ils surviennent d'une duplication locale ou segmentaire est écartée. En se concentrant sur l'humain et la souris, quelques analyses furent exécutées afin d'examiner davantage ces PRs. Plus de 200 PRs génomiques spécifiques furent identifiés dans la souris et le rat, comparés à ~40 dans chaque primates, humain et singe, indiquant que chez les rongeurs il y a plus d'activité récente de rétrotransposition génétique. La distribution de Ka/Ks pour les PRs humains est similaire à celle des rétropseudogènes humains. Cependant, quelques PRs de souris sont sous sélection purifiante, par l'évidence du fait qu'il y a un excès significatif de PRs de souris avec Ka/Ks < 0.5 comparé aux rétropseudogènes de souris.