The fluidity of plasma membranes of Dictyostelium discoideum. The effects of polyunsaturated fatty acid incorporation assessed by fluorescence depolarization and electron paramagnetic resonance

Abstract

Two probe techniques, fluorescence depolarization (using diphenylhexatriene) and electron paramagnetic resonance (using 5-doxyl stearic acid), have been used to assess the fluidity of the purified plasma membranes of Dictyostelium discoideum. Both techniques indicate that a large incorporation of polyunsaturated fatty acids into the plasma membranes does not significantly change membrane fluidity In addition, phosphatidylcholines isolated from cells grown on both polyunsaturated fatty acid-supplemented and unsupplemented media exhibit similar mobilities of an incorporated spin probe when dispersed in aqueous solution. This result suggests that the enrichment of a membrane already high in content of fatty acyl chains containing two double bonds with those containing three or more double bonds does not markedly change fluidity.