Molecular mechanism of lateral diffusion of py(10)-PC and free pyrene in fluid DMPC bilayers.
From the study of the kinetics of the fluorescence self-quenching of pyrene in multilamellar vesicles of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) in the fluid phase we obtain the molecular diffusion parameters, diffusion coefficients, and activation energies for lateral diffusion for three probes: 1-palmitoyl-2-(1-pyrenedecanoyl)-sn-glycero-3-phosphocholine (py(10)-PC), pyrene, and 1-pyrenebutanoic acid (py-but). The experiments are done in a range of temperatures for which the reversibility of excimer formation is negligible and the probe/phospholipid ratios used are low, avoiding non-ideal mixing of the probe. The time-resolved fluorescence decays are, in all cases, accurately and consistently described by the two-dimensional (2D) formalism for bimolecular diffusion-controlled reactions. From the parameters obtained in this way we conclude that the primary step of the diffusion of the pyrene-labeled phospholipid involves the simultaneous jump of phospholipid and fluorophore moieties, and also that although in the case of py(10)-PC the pyrene from molecules pertaining to different layers may interact during the lifetime of the exited state, this is not the case for free pyrene.
Martins
J
J
Instituto de Tecnologia Química e Biológica-UNL, Oeiras, Portugal.
Melo
E
E
D055592:Biophysical Phenomena; D001703:Biophysics; D004058:Diffusion; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry; D066298:In Vitro Techniques; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D008958:Models, Molecular; D010713:Phosphatidylcholines / Q000737:chemistry*; D011721:Pyrenes / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics
D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D011721:Pyrenes; C002218:1-pyrenebutyrate; C021248:1-palmitoyl-2-pyrenedecanoylphosphatidylcholine; C030984:pyrene; D004134:Dimyristoylphosphatidylcholine