The rotational motion of n-(9-Anthroyloxy) fatty acids in phospholipid bilayer vesicles

Abstract

The rotational motions of a set of n-(9-anthroyloxy) fatty acids (n = 2, 6, 9, 12) in dimyristoyl-phosphatidylcholine vesicles above and below the phase transition are investigated. Above the phase transition, single site occupancy and isotropic rotation of the fluorophores allows extraction and comparison of microviscosities from steady-state and time-resolved polarization measurements. Below the phase transition double exponential fluorescence and anisotropy decays are analysed in terms of microheterogeneity of sites. Comparison with previous reports indicates the caution needed when interpreting single photon counting data in terms of hindered rotational motions and order parameters.