title: Influence of vesicle curvature on fluorescence relaxation kinetics of fluorophores.
abstract: The effect of membrane curvature on the fluorescence decay of 2-p-toluidinyl-naphthalene-6-sulfonic acid (TNS), 2-(9-anthroyloxy) stearic acid (2-AS) and 12-(9-anthroyloxy)-stearic acid (12-AS) was investigated for egg lecithin vesicles of average diameter dm = 22 nm and 250 nm. The biexponential fluorescence decay of TNS at the red edge of the emission spectrum was analysed according to the model of Gonzalo and Montoro [1]. Over the entire temperature range (1-40 degrees C) the small TNS labelled vesicles showed significantly shorter solvent relaxation times tau(r) than their larger counterparts (e.g. 1.3 ns compared with 2.1 ns at 5 degrees C), indicating a higher mobility of the hydrated headgroups in the highly curved, small vesicles. The fluorescence decay of both AS derivatives is also biexponential. While the shorter decay times (1-3 ns) are practically identical for small and large vesicles, the longer decay times (5-14 ns) are identical only for 12-AS but not for 2-AS. This indicates that the microenvironment is similar in small and large vesicles deep in the membrane in spite of the differences in curvature.
authors.affiliation: Department of Physical Chemistry, Charles University, 128 40 Prague 2, Albertov 2030, Czech Republic.
authors.forename: M
authors.initials: M
authors.lastname: Hof
authors.forename: R
authors.initials: R
authors.lastname: Hutterer
authors.forename: N
authors.initials: N
authors.lastname: Pérez
authors.forename: H
authors.initials: H
authors.lastname: Ruf
authors.forename: F W
authors.initials: FW
authors.lastname: Schneider