No description available.

No description available.

Le bruissement enzymatiques, appelé mélanose post mortem chez les crustacés est un phénomène enzymatique catalysé par des protéines à activités phénoloxydases (tyronase, catécholase, laccase et hémocyanine). L'utilisation de conservateurs de type sulfites (E220 à E228 et E539) reste à l'heure actuelle la solution la plus répandue pour éviter le développement de cette coloration peu attrayante pour le consommateur. Mais une partie de la population développe des réactions d'hypersensibilité en consommant des aliments sulfités. Dans l'onbjectif de rechercher une alternative à ces conservateurs, deux axes de recherche ont été développés durant ces travaux de thèse : la caractérisation biochimique des protéines responsables de la mélanose post mortem chez la crevette P. monodon, puis la recherche de molécules inhibitrices. Un fractionnement sur résine Phenyl Sepahrose™ CL-4B (HIC) suivie d'une séparation par électrophorèse SDS-PAGE ont montré la présence de trois protéines de 46, 82 et 89 kDa à activité principalement laccase. Une identification par RP-HPLC-Q/TOF a mis en évidence la présence d'hémocyanine uniquement. Un pH de 7,0 et une température comprise entre 37 et 50 °C ont mis en évidence les activités les plus importantes, en utilisant le dosage enzymatique dit "test au MBTH". Par ailleurs, un criblage à haut débit de 45 molécules potentiellement inhibitrices a été réalisé dans des conditions d'analyses standardisées grâce à l'outil de robotique de la plateforme Realcat. Une inhibition a été mise en évidence pour 23 composés, certains étant suffisamment efficaces pour être utilisés seuls. D'autres pourraient être introduits dans un cocktail de molécules inhibitrices aux fonctionnalités complémentaires. Les résultats des tests de trempage réalisés sur des crevettes entières ont montré qu'il était indispensable de compléter les études in vitro avec des essais à l'échelle de la matrice alimentaire dans son intégralité. / Enzymatic browning, called post mortem melanosis in crustaceans, is an enzymatic phenomenon catalyzed by proteins with phenoloxidase activities (tyronase, catecholase, laccase and hemocyanin). The use of sulfite preservatives (E220 to E228 and E539) remains at present the most widespread solution to avoid the development of this unattractive color towards consumers. But, a part of the population develops hypersensitivity reactions by consuming sulfited foods. With the objective to find an alternative to these conversators, two research axes have been planned : the biochemical characterization of the proteins responsible for post mortem melanosis in the P. monodon shrimp, then the search for inhibitory molecules. Fractionation on Phenyl Sepahrose™ CL-4B resin (HIC) followed by SDS-PAGE electrophoresis separation showed the presence of three proteins of 46, 82 and 89 kDa with mainly laccase activity. Identification by RP-HPLC-Q / TOF revealed the presence of hemocyanin only. A pH of 7.0 and a temperature between 37 and 50 °C showed the most important activities, using the enzymatic assay called "MBTH test". On the other hand, a high throughput screening of 45 potentially inhibitory molecules could be performed under standardized analysis conditions thanks to the robotic tools of the Realcat platform

<div>The use of computational approaches to understand kinase substrate preference has been a powerful tool in the search to develop artificial peptide probes to monitor kinase activity, however, most of these efforts focus on a small portion of the human kinome. The use of high throughput techniques to identify known kinase substrates plays an important role in development of sensitive protein kinase activity assays.</div><div>The KINATEST-ID pipeline is an example of a computational tool that uses known kinase substrate sequence information to identify kinase substrate preference. This approach was used to design three artificial substrates for ABL, JAK2 and SRC family kinases. These biosensors were used to design ELISA and lanthanide-based assays to monitor in vitro kinase activity. The KINATEST-ID pipeline relies on a high number of reported kinase substrates to predict artificial substrate sequences, however, not all kinases have the sufficient number of known substrates to make an accurate prediction. </div><div>The adaptation of kinase assay linked with phosphoproteomics technique was used to increase the number of known FLT3 kinase variant substrate sequences. Subsequently, a set of data formatting tools were developed to curate the mass spectrometry data to become compatible with a command line version of the KINATEST-ID pipeline modules. This approach was used to design seven pan-FLT3 artificial substrate (FAStides) sequences. The pair of FAStides that were deemed the most sensitive toward FLT3 kinase phosphorylation were assayed in increasing concentrations of clinically relevant tyrosine kinase inhibitors. </div><div>To improve the automation of the mass spectrometry data analysis and formatting for use with the KINATEST-ID pipeline, a streamlined process was developed within a bioinformatic platform, GalaxyP. The data formatting tools used to process the FLT3 mass spectrometry data were converted into compatible versions to execute within the GalaxyP framework. This process was used to design four BTK artificial substrates (BAStide) to monitor kinase activity. Additionally, one of the BAStide sequences was designed in the lanthanide chelating motif to develop an antibody-free activity assay for BTK. </div><div>Lastly, a multicolored time resolved lanthanide assay was designed by labeling SYK artificial substrate and a SRC family artificial substrate to measure the activity of both kinases in the same kinase reaction. This highlighted the functionality of lanthanide-based time resolved assays for potential multiplexing assay development. </div><div><br></div>

The N-methyl-D-aspartate receptor (NMDAR) hypofunctional hypothesis is believed to explain one of the contributing factors to schizophrenia. This hypothesis suggests the dysregulation of NMDAR, a protein responsible for receiving signals from the synapses between neurons, is the cause of some of the symptoms seen in schizophrenia. The post synaptic density protein 95 (PSD95) uses its PDZ-domains to help facilitate the received signal from NMDAR to α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) which in turn transmits the signal through the neuron. One way to increase the function of NMDAR could be to increase its affinity towards PDZ-domains of PSD95 using a small molecule. Fragment based drug design (FBDD) is one way to screen for molecules that modulates the NMDAR-PDZ interaction. This work describes the development of differential scanning fluorimetry (DSF) and surface plasmon resonance (SPR) assays using a fusion protein to screen for molecules that potentiate the interaction between NMDAR and AMPAR as well as methods assisting in the prioritization of hits based on both affinity, selectivity, and mechanism. The developed assays were used to screen a library containing 768 compounds. Screen positives and other compounds of interest were triaged and evaluated based on affinity, selectivity, and ability to modulated peptide binding resulting in eight confirmed hits that interacts with the two PDZ-domains of PSD95 investigated. As part of this work, the dissociation constant (KD) was determined for a panel of peptides representing versions of the truncated NMDAR GluN2b-subunit C-terminal towards PDZ1 and 2 of PSD95.

No description available.

<p>This dissertation describes the effects of a <i>de novo</i> mutation of CaMKII found in children with learning disabilities and describes its effect on catalytic activity. We develop a malachite green assay for the measurement of CaMKII activation and use it for high-throughput chemical screening to identify CaMKII inhibitors and enhancers. We also propose a new mechanism of regulation of CaMKII activity by ADP.</p><p><br></p>