Membrane fluidity measured by fluorescence polarization using an EPICS V cell sorter

Abstract

We have characterized the measurement of fluorescence polarization on single cells using an EPICS V cell sorter. A critical analysis is made of the balancing and calibration of the system. The system is highly linear for polarization measurements. Cellular membranes were labeled with 1,6‐diphenyl‐1,3,5‐hexatriene (DPH) to measure membrane fluidity. Fluorescence polarization histograms had coefficients of variation as low as 7%. Cells labeled with DPH after 24 hr incubation in medium lacking serum showed a significantly higher fluorescence polarization than cells in medium containing serum. The fluorescence polarization measured at 15°C was 0.311 compared to 0.270 at 25°C for cells labeled with DPH, verifying that temperature affects the membrane fluidity as measured by flow cytometry. Copyright © 1987 Alan R. Liss, Inc.