title: Anomalous swelling of lipid bilayer stacks is caused by softening of the bending modulus.
abstract: Arrays of bilayers of the lipid dimyristoylphosphatidylcholine (DMPC) exhibit anomalous swelling as the temperature decreases from T=27 degrees C toward the main phase transition at T(M) =24 degrees C, within the fluid L(alpha) thermodynamic phase. Analysis of diffuse x-ray scattering data from oriented stacks of biological lipid bilayers now makes it possible to obtain the bending modulus K(C) and the bulk compressibility modulus B separately. We report results that show that the measured bending modulus K(C) for DMPC decreases by almost a factor of 2 between T=27 degrees C and the transition temperature at T(M) =24 degrees C, which is the same temperature range where the anomalous swelling occurs. We also report Monte Carlo simulations that show that the anomalous swelling can be fully accounted for by the measured decrease in K(C) with no changes in the van der Waals or hydration forces.
authors.affiliation: Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Nanjun
authors.initials: N
authors.lastname: Chu
authors.forename: Norbert
authors.initials: N
authors.lastname: Kucerka
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Liu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Tristram-Nagle
authors.forename: John F
authors.initials: JF
authors.lastname: Nagle
mesh_terms: D019245:Compressive Strength; D003198:Computer Simulation; D004134:Dimyristoylphosphatidylcholine / Q000032:analysis / Q000737:chemistry*; D004548:Elasticity; D008051:Lipid Bilayers / Q000737:chemistry*; D008560:Membrane Fluidity; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D013499:Surface Properties; D013696:Temperature
chemical_list: D008051:Lipid Bilayers; D004134:Dimyristoylphosphatidylcholine