Spatially-Resolved Fluorescence Spectra of Patterned Lipid Bilayers

Abstract

Planar supported lipid bilayers can be micropatterned such that the lipid composition of localized regions differ from that of the surrounding region. These micropatterned bilayers can serve as model systems to study the dynamics of microdomains in lipid bilayers. We have obtained spatially-resolved fluorescence spectra of bilayers patterned with alternating rows of 1% Rhodamine-DMPE/POPC and lipid voids with epifluorescence and TIRF (total internal reflection fluorescence) excitation. A 60X water immersion objective is used to image a 100-micron slice of the bilayer onto the entrance slit of an imaging spectrograph. A CCD camera at the exit port of the spectrograph records the fluorescence spectra from the bilayer. In conventional fluorescence spectroscopy, the signal from all the pixels of each column of the CCD camera, which corresponds to signal from a specific wavelength, is integrated to produce a single spectrum. In our experiment, such integration is not performed. Since the fluorescence spectra from the alternating rows of Rhodamine-DMPE/POPC and voids are imaged onto different rows of the CCD camera, their spectra can be spatially resolved.