Spatial correlation of lipid phase fluctuations in model membranes studied with two-photon fluorescence microscopy
Celli, Anna
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https://hdl.handle.net/2142/32104
Description
Title
Spatial correlation of lipid phase fluctuations in model membranes studied with two-photon fluorescence microscopy
Author(s)
Celli, Anna
Issue Date
2006-10
Director of Research (if dissertation) or Advisor (if thesis)
Gratton, E.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Biochemistry
Biophysics, General
lipid density fluctuations
fluorescence microscopy
Spatial correlation
membranes
Biomembranes
Giant Unilamellar Vesicles
Language
en
Abstract
The temporal dynamics of lipid phase fluctuations and the spatial organization of model lipid membranes was studied using Two-photon excitation fluorescence microscopy. Lipid membranes of different composition were reconstituted in Giant Unilamellar Vesicles (GUVs) and labeled with the environment sensitive dye LAURDAN whose spectral properties are sensitive to the lipid phase. The Generalized Polarization (GP) function was used to quantify the lipid phase state as detected by LAURDAN. Long lived micron sized structures were detected on membranes composed of a single lipid specie as the temperature was decreases towards the main (Liquid-crystalline to gel) phase transition by calculating the GP autocorrelation function of circular scanning measurements. In binary mixtures membranes, the influence of coexisting lipid species on the phase behavior of each other was detected and characterized comparing the experimental results with a simple two state approximation. High hydrostatic pressure was used to induce morphological transformation of the GUVs and study the coupling between mechanical stress and phase behavior of the membrane. The ability to visualize the morphological and phase behavior of single GUVs under the microscope has allowed studying the coupling between lipid phase and membrane curvature
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