title: A long-lived amphiphilic fluorescent probe studied in POPC air-water monolayer and solution bilayer systems.
abstract: A novel amphiphilic fluorescent probe (Fluorazophore-L) with a strongly dipolar, nonionic azoalkane as headgroup and a palmitoyl tail has been synthesized and characterized. Pure Fluorazophore-L was found to be sufficiently amphiphilic to form stable air-water monolayers. An analysis of the surface pressure versus area suggests an area per molecule of about 34+/-2 A(2) at 29 mN m(-1). The partitioning into a lipid membrane model was quantified at the air-water interface by spreading 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) monolayers. Measurements with different molar fractions of Fluorazophore-L revealed a small but significant reduction of the mean area in the mixed monolayer. The excess free energy of mixing (-0.5+/-0.1 kT) indicated a weakly attractive interaction slightly above thermal energy, suggesting a good miscibility of the fluorescent probe within the lipid monolayer without major structural modifications. Spectroscopic measurements confirmed the incorporation of Fluorazophore-L into POPC vesicles. The fluorescence lifetime was very long (125+/-5 ns under air) with monoexponential fluorescence decays.
authors.affiliation: Institut für Physikalische Chemie der Universität Basel, CH-4056 Basel, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Gramlich
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: M
authors.initials: M
authors.lastname: Winterhalter
authors.forename: W M
authors.initials: WM
authors.lastname: Nau
mesh_terms: D005456:Fluorescent Dyes / Q000138:chemical synthesis / Q000737:chemistry* / Q000493:pharmacokinetics; D008051:Lipid Bilayers / Q000737:chemistry*; D008823:Micelles; D008968:Molecular Conformation; D010713:Phosphatidylcholines / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013501:Surface-Active Agents / Q000737:chemistry / Q000493:pharmacokinetics; D013816:Thermodynamics
chemical_list: D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D008823:Micelles; D010713:Phosphatidylcholines; D013501:Surface-Active Agents; C028694:1-palmitoyl-2-oleoylphosphatidylcholine