M.Sc. Defence: Achebe N.O. Nzulumike
Achebe N.O. Nzulumike
Bio-Nanotechnology Laboratory, Department of Chemistry, University of Copenhagen
Tuesday, September 14th – 14:00
Aud. 5, HCØ, Universitetsparken 5
Title: Vesicle-Surface Interaction Studies via Single Particle Tracking - Quantitative Analysis
and Method Innovation
In this thesis, dynamics of fluorescently-labeled diffusing vesicles were quantitatively analyzed on the single particle level. Planar surfaces were biologically modified with either lipid bilayers or a heterogeneous protein composition, incubated with a population of vesicles, and followed by video acquisitions with a surface-sensitive fluorescence microscopy technique. The recorded micrographs were treated with single particle tracking, giving spatially and temporally resolved intensity traces for each detected vesicle.
Initially we studied intermembrane interaction in a model system with supported lipid bilayers as substrate, using particle tracking data to characterize different vesicle dynamic states. Distributions of dwell-times were derived, and it was shown that [Ca2+] has significant influence on vesicle mobility for phosphatidylserine-containing membranes.
The project developed into the establishment of a novel method for mapping interaction events, by consolidating particle tracking data in a fully encompassing array of binding sites. These maps provide coordinate-specific values of off-rates, on-rates, and interaction energy, and reveal interaction patterns that reflect protein composition on a heterogeneous surface. The method allows discrete regions to be identified and characterized by their interaction profile, using only passively diffusing vesicles that interact nonspecifically.