title: Relationship between the unbinding and main transition temperatures of phospholipid bilayers under pressure.
abstract: Using neutron diffraction and a specially constructed high pressure cell suitable for aligned multibilayer systems, we have studied, as a function of pressure, the much observed anomalous swelling regime in dimyristoyl- and dilauroyl-phosphatidylcholine bilayers, DMPC and DLPC, respectively. We have also reanalyzed data from a number of previously published experiments and have arrived at the following conclusions. (a). The power law behavior describing anomalous swelling is preserved in all PC bilayers up to a hydrostatic pressure of 240 MPa. (b). As a function of increasing pressure there is a concomitant decrease in the anomalous swelling of DMPC bilayers. (c). For PC lipids with hydrocarbon chains >or=13 carbons the theoretical unbinding transition temperature T small star, filled is coupled to the main gel-to-liquid crystalline transition temperature T(M). (d). DLPC is intrinsically different from the other lipids studied in that its T small star, filled is not coupled to T(M). (e). For DLPC bilayers we predict a hydrostatic pressure (>290 MPa) where unbinding may occur.
authors.affiliation: National Research Council, Steacie Institute for Molecular Sciences, Chalk River, Ontario, Canada K0J 1J0.
authors.forename: T A
authors.initials: TA
authors.lastname: Harroun
authors.forename: M-P
authors.initials: MP
authors.lastname: Nieh
authors.forename: M J
authors.initials: MJ
authors.lastname: Watson
authors.forename: V A
authors.initials: VA
authors.lastname: Raghunathan
authors.forename: G
authors.initials: G
authors.lastname: Pabst
authors.forename: M R
authors.initials: MR
authors.lastname: Morrow
authors.forename: J
authors.initials: J
authors.lastname: Katsaras
mesh_terms: D001665:Binding Sites; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D006874:Hydrostatic Pressure; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D008567:Membranes, Artificial; D008968:Molecular Conformation; D033363:Neutron Diffraction / Q000379:methods*; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry*; D010743:Phospholipids / Q000737:chemistry; D012996:Solutions; D044366:Transition Temperature
chemical_list: D005782:Gels; D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010713:Phosphatidylcholines; D010743:Phospholipids; D012996:Solutions; C002448:1,2-linoleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine