Cell membrane heterogeneity studied by camera-based fluorescence correlation spectroscopy
Simsek, Muhammed Fethullah
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The cell membrane is composed of a lipid bilayer and a protein meshwork structuring the membrane due to selective association of proteins with cholesterol stabilized lipid domains and protein clusters. These structures vary between cell types, during cell migration, and cancer cell progression. The membrane heterogeneity modulates cell communication and affect drug efficacy. In living cells, these structures are too small (~20 - 200 nm) and too dynamic (~10 - 100 ms) to be observed by diffraction limited optical microscopy. Correlation spectroscopy quantifies membrane protein diffusion in single living cells without perturbing the cells. We developed a camera-based correlation spectroscopy measuring this diffusion on multiple length-scales simultaneously distinguishing different types of membrane heterogeneity. I present data analysis for the technique and fitting algorithms for different diffusion modes of membrane proteins. I show how this is used to quantify changes in membrane structures on single cells in response to drug treatments, dimerization of molecules, changing extracellular conditions. I report single cell level membrane meshwork changes of in-situ to invasive progression of cancer cells by observation of epithelial to mesenchymal transition during on stage wound healing experiments and in response to physical and chemical differences of extracellular microenvironment. I also elucidate on how to model these membrane structures in computer simulations and estimate their physical and chemical features by matching the experiments with simulation results.