title: Oscillatory phase separation in giant lipid vesicles induced by transmembrane osmotic differentials.
abstract: Giant lipid vesicles are closed compartments consisting of semi-permeable shells, which isolate femto- to pico-liter quantities of aqueous core from the bulk. Although water permeates readily across vesicular walls, passive permeation of solutes is hindered. In this study, we show that, when subject to a hypotonic bath, giant vesicles consisting of phase separating lipid mixtures undergo osmotic relaxation exhibiting damped oscillations in phase behavior, which is synchronized with swell-burst lytic cycles: in the swelled state, osmotic pressure and elevated membrane tension due to the influx of water promote domain formation. During bursting, solute leakage through transient pores relaxes the pressure and tension, replacing the domain texture by a uniform one. This isothermal phase transition--resulting from a well-coordinated sequence of mechanochemical events--suggests a complex emergent behavior allowing synthetic vesicles produced from simple components, namely, water, osmolytes, and lipids to sense and regulate their micro-environment.
authors.affiliation: Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, Nanyang, Singapore.
authors.forename: Kamila
authors.initials: K
authors.lastname: Oglęcka
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Berkeley, Berkeley, United States.
authors.forename: Padmini
authors.initials: P
authors.lastname: Rangamani
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Nanyang, Singapore.
authors.forename: Bo
authors.initials: B
authors.lastname: Liedberg
authors.affiliation: Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, Nanyang, Singapore.
authors.forename: Rachel S
authors.initials: RS
authors.lastname: Kraut
authors.affiliation: School of Materials Science and Engineering, Nanyang Technological University, Nanyang, Singapore.
authors.forename: Atul N
authors.initials: AN
authors.lastname: Parikh
mesh_terms: D000818:Animals; D002645:Chickens; D006982:Hypertonic Solutions / Q000494:pharmacology; D007038:Hypotonic Solutions / Q000494:pharmacology; D008051:Lipid Bilayers / Q000737:chemistry*; D009995:Osmosis / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D044367:Phase Transition / Q000187:drug effects; D016062:Porosity; D053835:Unilamellar Liposomes / Q000737:chemistry*
chemical_list: D006982:Hypertonic Solutions; D007038:Hypotonic Solutions; D008051:Lipid Bilayers; D053835:Unilamellar Liposomes
keywords: biophysics; cell biology; compartmentalization; giant phospholipid vesicles; lipid rafts; phase separation; primitive osmoregulation; structural biology