Global ETD Search

281	Impact of cholesterol and Lumacaftor on the folding of CFTR helical hairpins Schenkel, Mathias, Ravamehr-Lake, Dorna, Czerniak, Tomasz, Saenz, James P., Krainer, Georg, Schlierf, Michael, Deber, Charles M. 07 December 2023 (has links) Cystic fibrosis (CF) is caused by mutations in the gene that codes for the chloride channel cystic fibrosis transmembrane conductance regulator (CFTR). Recent advances in CF treatment have included use of small-molecule drugs known as modulators, such as Lumacaftor (VX-809), but their detailed mechanism of action and interplay with the surrounding lipid membranes, including cholesterol, remain largely unknown. To examine these phenomena and guide future modulator development, we prepared a set of wild type (WT) and mutant helical hairpin constructs consisting of CFTR transmembrane (TM) segments 3 and 4 and the intervening extracellular loop (termed TM3/4 hairpins) that represent minimal membrane protein tertiary folding units. These hairpin variants, including CF-phenotypic loop mutants E217G and Q220R, and membrane-buried mutant V232D, were reconstituted into large unilamellar phosphatidylcholine (POPC) vesicles, and into corresponding vesicles containing 70 mol% POPC +30 mol% cholesterol, and studied by single-molecule FRET and circular dichroism experiments. We found that the presence of 30 mol% cholesterol induced an increase in helicity of all TM3/4 hairpins, suggesting an increase in bilayer cross-section and hence an increase in the depth of membrane insertion compared to pure POPC vesicles. Importantly, when we added the corrector VX-809, regardless of the presence or absence of cholesterol, all mutants displayed folding and helicity largely indistinguishable from the WT hairpin. Fluorescence spectroscopy measurements suggest that the corrector alters lipid packing and water accessibility. We propose a model whereby VX-809 shields the protein from the lipid environment in a mutant-independent manner such that the WT scaffold prevails. Such ‘normalization’ to WT conformation is consistent with the action of VX-809 as a protein-folding chaperone. info:eu-repo/classification/ddc/570 ddc:570
282	Synthese, biologische Evaluation und Untersuchung des Wirkmechanismus neuartiger Duocarmycin-Analoga für eine selektive Krebstherapie / Synthesis, Biological Evaluation and Investigation of the Mode of Action of Novel Anti-Tumour Agents for a Selective Cancer Therapy Krewer, Birgit 22 January 2009 (has links) No description available. 540 Chemie Mathematics and Computer Science ADEPT Tumortherapie Prodrug CC-1065 Duocarmycine DNA Massenspektrometrie Chromatographie Circular Dichroismus Wirkmechanismus ADEPT tumor therapy prodrug CC-1065 duocarmycin DNA mass spectrometry chromatography Circular Dichroism mechanism of action 35.26 35.29 35.33 35.59 35.71 35.75 35.52 44.33
283	Etude des dynamiques moléculaires sondées par générations d'harmoniques d'ordres élevés / Studies of molecular dynamics probed by High Harmonic Generation Ferré, Amelie 03 October 2014 (has links) Grâce à ses propriétés (cohérence, brillance, durée), le rayonnement XUV femtoseconde produit par génération d'harmoniques d'ordre élevé est utilisé comme un processus de sonde pour l'étude de dynamiques atomiques et moléculaires, avec une bonne résolution spatiale et temporelle (femtoseconde voire attoseconde). Ainsi, des dynamiques rotationnelles ont été résolues sur des petits systèmes moléculaires (N2, CO2). Les travaux de cette thèse ont consisté à étendre les méthodes de spectroscopie harmoniques et les appliquer à des systèmes moléculaires complexes d'intérêt femtochimique. Parmi elles, nous présenterons la génération d'harmoniques à deux sources, le réseau transitoire d'excitation ou encore la génération d'harmoniques à deux couleurs. Ces techniques nous ont permis de résoudre des dynamiques femtosecondes dans N2O4 et SF6. La HHG est aussi utilisée comme source de rayonnement XUV, en jouant le rôle d'impulsion pompe lors d'expériences de type pompe-sonde. Cette approche a été utilisée pour l'étude du dichroïsme circulaire de photoélectrons de molécules chirales ionisées par un champ XUV harmonique de polarisation quasi circulaire. Nous nous attarderons à détailler la découverte de cette nouvelle source XUV femtoseconde de polarisation quasi circulaire. / High harmonic generation (HHG) spectroscopy has proven to be a promisingtool (like probe in pump-probe experiments) in revealing the atomic and molecular dynamicswith the potential for subangstrom spatial resolution and subfemtosecond temporalresolution. Then, rotational dynamics have been resolved on small molecular systems (N2,CO2). This thesis looks to extending HHG spectroscopy methods to probe the structureand the dynamic of complex molecular systems. We will describe the two sources highharmonic generation, the transient grating of excitation and the two-color high harmonicgeneration. We enable to resolve the femtosecond nuclear dynamics in N2O4 and SF6. HHGis also used like a XUV radiation source, playing the role of pump pulse. This approach hasbeen used for the study of photoelectron circular dichroism. An XUV harmonic field witha quasi-circular polarization ionizes chiral molecules. In this manuscript, we will developthis new femtosecond XUV and quasi circular polarization radiation. Interaction laser-matière Spectroscopie harmonique Attoseconde Résonances Polarimétrie XUV Imagerie de vecteur vitesse Ionisation au-dessus du seuil Molécules chirales Laser-matter interaction High harmonic generation Atomic and molecular femtosecond physics Attosecond Resonances XUV Polarimetry Velocity Map Imaging Photoelectron Spectrometry Above Threshold Ionization Chiral molecules Photoelectron Circular Dichroism
284	Untersuchungen von inter- und intramolekularen Interaktionen des globalen Regulators AbrB und dessen Antirepressors AbbA Neubauer, Svetlana 16 January 2014 (has links) Aus den frühen Bindungsstudien des globalen Regulators AbrB mit der ausgedehnten phyC-Promotorregion von Bacillus amyloliquefaciens FZB45 konnte ein mehrstufiger kooperativer Bindungsprozess abgeleitet werden. Dabei verlangt die AbrB-vermittelte Repression von phyC nach Integrität zweier großer Bindungsstellen, ABS1 und ABS2, die 162 bp voneinander entfernt liegen. In der vorliegenden Arbeit wurden die ersten Echtzeitkinetiken zur DNA-AbrB-Interaktion mittels der Oberflächenplasmonresonanz (SPR) gemessen und analysiert. AbrB zeigte hohe Affinitäten zu den 40 bp langen Oligonukleotiden, die den beiden Bindungsstellen entstammen. Dabei verursachten alle Oligonukleotide der ABS2 und nur eine kurze Region innerhalb der ABS1 bei der Bindung von AbrB Konformationsänderungen im Protein und in der DNA (CD - Zirkulardichroismusspektroskopie) und wiesen eine Kooperativität von 2 / In previous binding studies it could be demonstrated that a global regulator AbrB and the extensive phyC promoter region of Bacillus amyloliquefaciens FZB45 interact in a complex manner. AbrB binding is a multistep cooperative process. The integrity of both binding sites, ABS1 and ABS2, which are separated by 162 bp, is crucial for the AbrB-mediated repression of phyC. This work presents the first real-time binding kinetics of the AbrB-DNA interaction using surface plasmon resonance (SPR). AbrB exhibited high affinities to all analyzed 40-bp oligonucleotides that were derived from the ABSs of phyC. All parts of the ABS2, but only a small region within ABS1, were bound cooperatively to AbrB with a stoichiometry of 2 DNA to 1 AbrB tetramer and with 2 Mutagenese AbrB AbbA phyC-Promotor Protein-DNA-Interaktion Bacillus amyloliquefaciens FZB45 Oberflächenplasmonresonanz (SPR) Echtzeitbindungskinetiken positive Kooperativität negative Kooperativität Hill-Koeffizient Gleichgewichtskonstante der Dissoziation Zirkulardichroismus (CD) chemische Interferenzfootprints Röntgenkleinwinkelstreuung (SAXS) Alaninsubstitution Gelretardationsassays (EMSA) in vitro Transkription mutagenesis AbrB AbbA phyC-promoter protein-DNA interaction Bacillus amyloliquefaciens FZB45 surface plasmon resonance (SPR) real-time binding kinetics positive cooperativity negative cooperativity Hill-coefficient equilibrium dissociation constant circular dichroism (CD) chemical interference footprints small angle X-ray scattering (SAXS) alanine substitution gel retardation assays (EMSA) in vitro transcription 570 Biowissenschaften, Biologie 32 Biologie WG 4050 ddc:570

Page generated in 0.0488 seconds