title: Calcium modulates the mechanical properties of anionic phospholipid membranes.
abstract: Using micropipette aspiration and fluorescence techniques, we have studied the material properties of charged lipid vesicles in calcium solutions. Vesicles were composed of phosphatidylglycerol (PG)/phosphatidylcholine (PC) or phosphatidic acid (PA)/PC mixtures. For the case of PG/PC membranes, we measure no effect of anionic lipid fraction on elasticity but a monotonic decrease up to 20% for tension required to induce membrane failure. Both of these observations are rationalized by a model we have developed to describe membrane electrostatic interactions in a two-component salt solution and the resulting changes in membrane properties. Critical tensions measured for PA/PC membranes, on the other hand, did not depend on anionic lipid fraction and were uniformly approximately 35% lower than PG/PC vesicles. This is likely due to a lateral phase separation in the membrane. By combining mechanical properties with fluorescence observations we propose that the PA-rich phase separates into small unconnected domains.
authors.affiliation: Department of Chemical Engineering, Princeton University, Princeton, NJ 08544, USA.
authors.forename: Scott D
authors.initials: SD
authors.lastname: Shoemaker
authors.forename: T Kyle
authors.initials: TK
authors.lastname: Vanderlick
mesh_terms: D000838:Anions; D001696:Biomechanical Phenomena; D002118:Calcium / Q000737:chemistry*; D004548:Elasticity; D004573:Electrolytes; D008563:Membrane Lipids / Q000737:chemistry; D008567:Membranes, Artificial; D010712:Phosphatidic Acids / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry; D010715:Phosphatidylglycerols / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D012492:Salts; D012996:Solutions; D013050:Spectrometry, Fluorescence
chemical_list: D000838:Anions; D004573:Electrolytes; D008563:Membrane Lipids; D008567:Membranes, Artificial; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010715:Phosphatidylglycerols; D010743:Phospholipids; D012492:Salts; D012996:Solutions; D002118:Calcium