title: Experimental Estimation of Membrane Tension Induced by Osmotic Pressure.
abstract: Osmotic pressure (Π) induces the stretching of plasma membranes of cells or lipid membranes of vesicles, which plays various roles in physiological functions. However, there have been no experimental estimations of the membrane tension of vesicles upon exposure to Π. In this report, we estimated experimentally the lateral tension of the membranes of giant unilamellar vesicles (GUVs) when they were transferred into a hypotonic solution. First, we investigated the effect of Π on the rate constant, kp, of constant-tension (σex)-induced rupture of dioleoylphosphatidylcholine (DOPC)-GUVs using the method developed by us recently. We obtained the σexdependence of kpin GUVs under Π and by comparing this result with that in the absence of Π, we estimated the tension of the membrane due to Π at the swelling equilibrium, σosmeq. Next, we measured the volume change of DOPC-GUVs under small Π. The experimentally obtained values of σosmeqand the volume change agreed with their theoretical values within the limits of the experimental errors. Finally, we investigated the characteristics of the Π-induced pore formation in GUVs. The σosmeqcorresponding to the threshold Π at which pore formation is induced is similar to the threshold tension of the σex-induced rupture. The time course of the radius change of GUVs in the Π-induced pore formation depends on the total membrane tension, σt; for small σt, the radius increased with time to an equilibrium one, which remained constant for a long time until pore formation, but for large σt, the radius increased with time and pore formation occurred before the swelling equilibrium was reached. Based on these results, we discussed the σosmeqand the Π-induced pore formation in lipid membranes.
authors.affiliation: Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka, Japan.
authors.forename: Sayed Ul
authors.initials: SU
authors.lastname: Alam Shibly
authors.affiliation: Nanomaterials Research Division, Research Institute of Electronics, Shizuoka University, Shizuoka, Japan.
authors.forename: Chiranjib
authors.initials: C
authors.lastname: Ghatak
authors.affiliation: Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka, Japan.
authors.forename: Mohammad Abu
authors.initials: MA
authors.lastname: Sayem Karal
authors.affiliation: Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka, Japan.
authors.forename: Md
authors.initials: M
authors.lastname: Moniruzzaman
authors.affiliation: Integrated Bioscience Section, Graduate School of Science and Technology, Shizuoka University, Shizuoka, Japan; Nanomaterials Research Division, Research Institute of Electronics, Shizuoka University, Shizuoka, Japan; Department of Physics, Faculty of Science, Shizuoka University, Shizuoka, Japan. Electronic address: yamazaki.masahito@shizuoka.ac.jp.
authors.forename: Masahito
authors.initials: M
authors.lastname: Yamazaki
mesh_terms: D002462:Cell Membrane / Q000737:chemistry* / Q000378:metabolism; D007700:Kinetics; D009997:Osmotic Pressure; D010713:Phosphatidylcholines / Q000737:chemistry; D013395:Sucrose / Q000378:metabolism; D053835:Unilamellar Liposomes / Q000737:chemistry / Q000378:metabolism
chemical_list: D010713:Phosphatidylcholines; D053835:Unilamellar Liposomes; D013395:Sucrose; C017251:1,2-oleoylphosphatidylcholine