title: Time-resolved and equilibrium measurements of the effects of poly(ethylene glycol) on small unilamellar phospholipid vesicles.
abstract: The effects of poly(ethylene glycol) (PEG) on sonicated unilamellar vesicles made of phosphatidylcholine have been examined. Stopped-flow and equilibrium data are presented for vesicle aggregation, vesicle leakage, lipid mixing, and aqueous contents mixing. Vesicle aggregation is detected as a monoexponential increase in light scattering, for PEG concentrations between 5 and 10%. In the region between 10-15% and 23-27% PEG, under our experimental conditions, the increase in light scattering follows a more complex biexponential kinetics, and, under these conditions, vesicle aggregation is accompanied by lipid mixing, a combination of events denoted as "close apposition". Above 23-27% PEG, the increase in light scattering is accompanied by fast lipid mixing, and also mixing of aqueous contents, all this being indicative of vesicle fusion; in addition, leakage occurs under these circumstances. Fusion takes place at high PEG concentrations, as indicated above, without any dilution step. From a methodological point of view, the Tb/DPA assay is shown to be more appropriate than the ANTS/DPX method for leakage and fusion studies in the presence of PEG.
authors: Department of Biochemistry, University of the Basque Country, Bilbao, Spain.
authors: A R
authors: AR
authors: Viguera
authors: M
authors: M
authors: Mencía
authors: F M
authors: FM
authors: Goñi
mesh_terms: D004735:Energy Transfer; D007700:Kinetics; D008027:Light; D008081:Liposomes / Q000737:chemistry* / Q000378:metabolism; D008561:Membrane Fusion; D009281:Naphthalenes; D010713:Phosphatidylcholines / Q000737:chemistry; D010848:Picolinic Acids; D011092:Polyethylene Glycols / Q000494:pharmacology*; D011726:Pyridinium Compounds; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence; D013725:Terbium; D014992:Xylenes
chemical_list: D008081:Liposomes; D009281:Naphthalenes; D010713:Phosphatidylcholines; D010848:Picolinic Acids; D011726:Pyridinium Compounds; D014992:Xylenes; D013725:Terbium; D011092:Polyethylene Glycols; C046465:8-amino-1,3,6-naphthalenetrisulfonic acid; C004860:dipicolinic acid