title: Structure and water permeability of fully hydrated diphytanoylPC.
abstract: Diphytanoylphosphatidylcholine (DPhyPC) is a branched chain lipid often used for model membrane studies, including peptide/lipid interactions, ion channels and lipid rafts. This work reports results of volume measurements, water permeability measurements P(f), X-ray scattering from oriented samples, and X-ray and neutron scattering from unilamellar vesicles at T=30 degrees C. We measured the volume/lipid V(L)=1426+/-1A(3). The area/lipid was found to be 80.5+/-1.5A(2) when both X-ray and neutron data were combined with the SDP model analysis (Kucerka, N., Nagle, J.F., Sachs, J.N., Feller, S.E., Pencer, J., Jackson, A., Katsaras, J., 2008. Lipid bilayer structure determined by the simultaneous analysis of neutron and X-ray scattering data. Biophys. J. 95, 2356-2367); this is substantially larger than the area of DOPC which has the largest area of the common linear chain lipids. P(f) was measured to be (7.0+/-1.0)x10(-3)cm/s; this is considerably smaller than predicted by the recently proposed 3-slab model (Nagle, J.F., Mathai, J.C., Zeidel, M.L., Tristram-Nagle, S., 2008. Theory of passive permeability through lipid bilayers. J. Gen. Physiol. 131, 77-85). This disagreement can be understood if there is a diminished diffusion coefficient in the hydrocarbon core of DPhyPC and that is supported by previous molecular dynamics simulations (Shinoda, W., Mikami, M., Baba, T., Hato, M., 2004. Molecular dynamics study on the effects of chain branching on the physical properties of lipid bilayers. 2. Permeability. J. Phys. Chem. B 108, 9346-9356). While the DPhyPC head-head thickness (D(HH)=36.4A), and Hamaker parameter (H=4.5x10(-21)J) were similar to the linear chain lipid DOPC, the bending modulus (K(C)=5.2+/-0.5x10(-21)J) was 30% smaller. Our results suggest that, from the biophysical perspective, DPhyPC belongs to a different family of lipids than phosphatidylcholines that have linear chain hydrocarbon chains.
authors.affiliation: Biological Physics Group, Physics, Carnegie Mellon University, Pittsburgh, PA 15213, United States. stn@cmu.edu
authors.forename: Stephanie
authors.initials: S
authors.lastname: Tristram-Nagle
authors.forename: Dong Joo
authors.initials: DJ
authors.lastname: Kim
authors.forename: Nadia
authors.initials: N
authors.lastname: Akhunzada
authors.forename: Norbert
authors.initials: N
authors.lastname: Kucerka
authors.forename: John C
authors.initials: JC
authors.lastname: Mathai
authors.forename: John
authors.initials: J
authors.lastname: Katsaras
authors.forename: Mark
authors.initials: M
authors.lastname: Zeidel
authors.forename: John F
authors.initials: JF
authors.lastname: Nagle
mesh_terms: D008051:Lipid Bilayers / Q000737:chemistry; D033363:Neutron Diffraction; D010539:Permeability; D010713:Phosphatidylcholines / Q000737:chemistry* / Q000378:metabolism; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D014867:Water; C021016:1,2-diphytanoylphosphatidylcholine
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