Microscopic Imaging of Phase Separation in Giant Liposome by Using Laurdan at Video Rate

概要

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Laurdan is a useful fluorescence dye for observation of physical properties of membranes. An optical system was constructed in order to image generalized polarization (GP), that characterizes the change of the spectrum of laurdan. The fluorescence images through the optical system were recorded on a digital video recorder and the images were processed to GP images, which made it possible to measure the spatial distribution of membrane fluidity quantitatively at video rate. Using this imaging instrument, the change of membrane fluidity at every moment of phase transition was observed in a giant liposome of pure dimyristoylphosphatidylcholine and the dynamics of phase separation was observed in a giant liposome composed of dimyristoylphosphatidylcholine and dimyristoylphosphatidylethanolamine after an annealing process. A clear phase separation was observed in the giant liposome in the cooling process from 43 to 40°C. The GP value of the phase-separated region on the liposome was related to the shape of the same region. The linear part of the liposome had a high GP value and the hinge part had a low GP value.
2005-12-15