Characterizing the kinetics of human ligand-receptor interactions with single molecule sensitivity
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Applied physics (MPAPP), MSc
Publicerad
2012
Författare
Wahlsten, Olov
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
Membrane proteins represent about two thirds of the protein targets for existing drugs. Therefore, studies of this class of proteins is a very important part of the drug discovery process. Large drug developing companies put enormous resources on getting new products into the market, motivating new and more efficient means for the characterization of potential drugs. In this thesis a method with single molecule sensitivity is investigated for the characterization of the interaction between a G-Protein Coupled Receptor (GPCR) and one of its natural ligands. GPCRs are estimated to be targeted by more than 40% of the drugs used in clinical medicine, making them the pharmaceutically most important subclass of membrane proteins. In this project the CXCR3 receptor is studied along with its chemokine ligand CXCL10. This receptor-ligand couple plays an important role in our immune system and diseases such as multiple sclerosis and type 1 diabetes are related to the CXCR3 receptor. The approach is to immobilize ligands on a surface and use fluorescently labeled vesicles, derived from membranes of cells expressing the CXCR3 transmembrane protein, in order to visualize the ligand-receptor interaction. The initial evaluation of the surface chemistry was performed with the Quartz Crystal Microbalance with Dissipation monitoring (QCMD) technique. Bind and release events between receptor and ligand were monitored under equilibrium with single event resolution using Total Internal Reflection Fluorescence Microscopy (TIRFM). Kinetic parameters characterizing the interaction were extracted from statistics on these bind and release events. koff and kon for the interaction between the CXCR3 receptor and the CXCL10 ligand were determined to 6:7 10 4 s 1 and 4:0 104 1M 1, respectively. The equilibrium dissociation constant, Kd, was determined implicitly to 16:8 nM and theoretically to 0:3 nM.
Beskrivning
Ämne/nyckelord
Biofysik , Biophysics