title: Lipid bilayers and membrane dynamics: insight into thickness fluctuations.
abstract: Thickness fluctuations have long been predicted in biological membranes but never directly observed experimentally. Here, we utilize neutron spin echo spectroscopy to experimentally reveal such fluctuations in a pure, fully saturated, phosphocholine lipid bilayer system. These fluctuations appear as an excess in the dynamics of undulation fluctuations. Like the bending rigidity, the thickness fluctuations change dramatically as the lipid transition temperature is crossed, appearing to be completely suppressed below the transition. Above the transition, the relaxation rate is on the order of 100 ns and is independent of temperature. The amplitude of the thickness fluctuations is 3.7 Å ± 0.7 Å, which agrees well with theoretical calculations and molecular dynamics simulations. The dependence of the fluctuations on lipid tail lengths is also investigated and determined to be minimal in the range of 14 to 18 carbon tails.
authors.affiliation: NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-6102, USA.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Woodka
authors.forename: Paul D
authors.initials: PD
authors.lastname: Butler
authors.forename: Lionel
authors.initials: L
authors.lastname: Porcar
authors.forename: Bela
authors.initials: B
authors.lastname: Farago
authors.forename: Michihiro
authors.initials: M
authors.lastname: Nagao
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry*; D008566:Membranes / Q000737:chemistry*; D008567:Membranes, Artificial; D056004:Molecular Dynamics Simulation; D033363:Neutron Diffraction / Q000379:methods; D044367:Phase Transition; D010713:Phosphatidylcholines / Q000737:chemistry; D053838:Scattering, Small Angle
chemical_list: D008051:Lipid Bilayers; D008567:Membranes, Artificial; D010713:Phosphatidylcholines