Effect of phase transitions in hydrated 1,2-dipalmitoylphosphatidylethanolamine bilayers on the spin probe order parameter

AbstractThe ‘main’ phase transition Lβ→Lα of hydrated 1,2-dipalmitoylphosphatidylethanolamine (DPPE) bilayers in excess water affects the ESR order parameter S33 of N-cetyl-N,N-dimethyl-N-tempoylammonium bromide (CAT-16), 5-doxylstearic acid (5-DSA) and 16-doxylstearic acid (16-DSA) spin probes. The ‘pretransition’ and ‘subtransition’ suggested to occur in hydrated DPPE by Chowdhry et al. [(1984) Biophys. J. 45, 901–904] and Silvius et al. [(1986) Biochemistry 25, 4249–4258], respectively, affect exclusively the S33 of CAT-16, but not that of 5-DSA and 16-DSA spin probes. The subtransition occurs about 15 ± 1°C below the main transition