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Full-Text Articles in Physical Sciences and Mathematics
Preparation Of Oriented, Fully Hydrated Lipid Samples For Structure Determination Using X-Ray Scattering., Stephanie Tristram-Nagle
Preparation Of Oriented, Fully Hydrated Lipid Samples For Structure Determination Using X-Ray Scattering., Stephanie Tristram-Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This chapter describes a method of sample preparation called "the rock and roll method," which is basically a solvent evaporation technique with controlled manual sample movement during evaporation of solvent from lipid/solvent mixtures that produces well-oriented thick stacks of about 2000 lipid bilayers. Many lipid types have been oriented using different solvent mixtures that balance solubilization of the lipid with uniform deposition of the lipid solution onto solid substrates. These well-oriented thick stacks are then ideal samples for collection of both X-ray diffraction data in the gel phase and X-ray diffuse scattering data in the fluid phase of lipids. The …
Structure And Water Permeability Of Fully Hydrated Diphytanoylpc., Stephanie Tristram-Nagle, Dong Joo Kim, Nadia Akhunzada, Norbert Kucerka, John Mathai, John Katsaras, Mark Zeidel, John Nagle
Structure And Water Permeability Of Fully Hydrated Diphytanoylpc., Stephanie Tristram-Nagle, Dong Joo Kim, Nadia Akhunzada, Norbert Kucerka, John Mathai, John Katsaras, Mark Zeidel, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
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 …
Structure Of Lipid Bilayers, John Nagle, Stephanie Tristram-Nagle
Structure Of Lipid Bilayers, John Nagle, Stephanie Tristram-Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
The quantitative experimental uncertainty in the structure of fully hydrated, biologically relevant, fluid (L(alpha)) phase lipid bilayers has been too large to provide a firm base for applications or for comparison with simulations. Many structural methods are reviewed including modern liquid crystallography of lipid bilayers that deals with the fully developed undulation fluctuations that occur in the L(alpha) phase. These fluctuations degrade the higher order diffraction data in a way that, if unrecognized, leads to erroneous conclusions regarding bilayer structure. Diffraction measurements at high instrumental resolution provide a measure of these fluctuations. In addition to providing better structural determination, this …
Thermodynamic And Structural Characterization Of Amino Acid-Linked Dialkyl Lipids., Stephanie Tristram-Nagle, Ruthven Lewis, Joseph Blickenstaff, Michael Diprima, Bruno Marques, Ronald Mcelhaney, John Nagle, James Schneider
Thermodynamic And Structural Characterization Of Amino Acid-Linked Dialkyl Lipids., Stephanie Tristram-Nagle, Ruthven Lewis, Joseph Blickenstaff, Michael Diprima, Bruno Marques, Ronald Mcelhaney, John Nagle, James Schneider
Prof. Stephanie Tristram-Nagle Ph.D.
Using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), we determined some thermodynamic and structural parameters for a series of amino acid-linked dialkyl lipids containing a glutamic acid-succinate headgroup and di-alkyl chains: C12, C14, C16 and C18 in CHES buffer, pH 10. Upon heating, DSC shows that the C12, C14 and annealed C16 lipids undergo a single transition which XRD shows is from a lamellar, chain ordered subgel phase to a fluid phase. This single transition splits into two transitions for C18, and FTIR shows that the upper main transition is predominantly the melting of …
Hiv Fusion Peptide Penetrates, Disorders, And Softens T-Cell Membrane Mimics., Stephanie Tristram-Nagle, Rob Chan, Edgar Kooijman, Pradeep Uppamoochikkal, Wei Qiang, David Weliky, Pradeep Uppamoochikkal
Hiv Fusion Peptide Penetrates, Disorders, And Softens T-Cell Membrane Mimics., Stephanie Tristram-Nagle, Rob Chan, Edgar Kooijman, Pradeep Uppamoochikkal, Wei Qiang, David Weliky, Pradeep Uppamoochikkal
Prof. Stephanie Tristram-Nagle Ph.D.
This work investigates the interaction of N-terminal gp41 fusion peptide (FP) of human immunodeficiency virus type 1 (HIV-1) with model membranes in order to elucidate how FP leads to fusion of HIV and T-cell membranes. FP constructs were (i) wild-type FP23 (23 N-terminal amino acids of gp41), (ii) water-soluble monomeric FP that adds six lysines on the C-terminus of FP23 (FPwsm), and (iii) the C-terminus covalently linked trimeric version (FPtri) of FPwsm. Model membranes were (i) LM3 (a T-cell mimic), (ii) 1,2-dioleoyl-sn-glycero-3-phosphocholine, (iii) 1,2-dioleoyl-sn-glycero-3-phosphocholine/30 mol% cholesterol, (iv) 1,2-dierucoyl-sn-glycero-3-phosphocholine, and (v) 1,2-dierucoyl-sn-glycero-3-phosphocholine/30 mol% cholesterol. Diffuse synchrotron low-angle x-ray scattering from fully …
Orientation Of Tie-Lines In The Phase Diagram Of Dopc/Dppc/Cholesterol Model Biomembranes., Pradeep Uppamoochikkal, Stephanie Tristram-Nagle, John Nagle
Orientation Of Tie-Lines In The Phase Diagram Of Dopc/Dppc/Cholesterol Model Biomembranes., Pradeep Uppamoochikkal, Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
We report the direction of tie-lines of coexisting phases in a ternary diagram of DOPC/DPPC/cholesterol lipid bilayers, which has been a system of interest in the discussion of biological rafts. For coexisting Ld and Lo phases, we find that the orientation angle α of the tie-lines increases as the cholesterol concentration increases and it also increases as temperature increases from T = 15 °C to T = 30 °C. Results at lower cholesterol concentrations support the existence of a different two-phase coexistence region of Ld and So phases and the existence of a three-phase region separating the two two-phase regions. …
Alamethicin Aggregation In Lipid Membranes., Jianjun Pan, Stephanie Tristram-Nagle, John Nagle
Alamethicin Aggregation In Lipid Membranes., Jianjun Pan, Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
X-ray scattering features induced by aggregates of alamethicin (Alm) were obtained in oriented stacks of model membranes of DOPC(diC18:1PC) and diC22:1PC. The first feature obtained near full hydration was Bragg rod in-plane scattering near 0.11 A(-1) in DOPC and near 0.08 A(-1) in diC22:1PC at a 1:10 Alm:lipid ratio. This feature is interpreted as bundles consisting of n Alm monomers in a barrel-stave configuration surrounding a water pore. Fitting the scattering data to previously published molecular dynamics simulations indicates that the number of peptides per bundle is n = 6 in DOPC and n >or= 9 in diC22:1PC. The larger …
Lipid Bilayers: Thermodynamics, Structure, Fluctuations, And Interactions., Stephanie Tristram-Nagle, John Nagle
Lipid Bilayers: Thermodynamics, Structure, Fluctuations, And Interactions., Stephanie Tristram-Nagle, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This article, adapted from our acceptance speech of the Avanti Award in Lipids at the 47th Biophysical Society meeting in San Antonio, 2003, summarizes over 30 years of research in the area of lipid bilayers. Beginning with a theoretical model of the phase transition (J.F.N.), we have proceeded experimentally using dilatometry and density centrifugation to study volume, differential scanning calorimetry to study heat capacity, and X-ray scattering techniques to study structure of lipid bilayers as a function of temperature. Electron density profiles of the gel and ripple phases have been obtained as well as profiles from several fluid phase lipids, …
Crac Motif Peptide Of The Hiv-1 Gp41 Protein Thins Sopc Membranes And Interacts With Cholesterol., Alexander Greenwood, Jianjun Pan, Thalia Mills, John Nagle, Richard Epand, Stephanie Tristram-Nagle
Crac Motif Peptide Of The Hiv-1 Gp41 Protein Thins Sopc Membranes And Interacts With Cholesterol., Alexander Greenwood, Jianjun Pan, Thalia Mills, John Nagle, Richard Epand, Stephanie Tristram-Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This study uses low-angle (LAXS) and wide-angle (WAXS) X-ray synchrotron scattering, volume measurements and thin layer chromatography to determine the structure and interactions of SOPC, SOPC/cholesterol mixtures, SOPC/peptide and SOPC/cholesterol/peptide mixtures. N-acetyl-LWYIK-amide (LWYIK) represents the naturally-occurring CRAC motif segment in the pretransmembrane region of the gp41 protein of HIV-1, and N-acetyl-IWYIK-amide (IWYIK), an unnatural isomer, is used as a control. Both peptides thin the SOPC bilayer by approximately 3 A, and cause the area/unit cell (peptide+SOPC) to increase by approximately 9 A2 from the area/lipid of SOPC at 30 degrees C (67.0+/-0.9 A2). Model fitting suggests that LWYIK's average position …
Polymorphism In Myristoylpalmitoylphosphatidylcholine., Stephanie Tristram-Nagle, Yisrael Isaacson, Yulia Lyatskaya, Yufeng Liu, Kay Brummond, John Katsaras, John Nagle
Polymorphism In Myristoylpalmitoylphosphatidylcholine., Stephanie Tristram-Nagle, Yisrael Isaacson, Yulia Lyatskaya, Yufeng Liu, Kay Brummond, John Katsaras, John Nagle
Prof. Stephanie Tristram-Nagle Ph.D.
This study focuses on the mixed-chain lipid myristoylpalmitoylphosphatidylcholine (MPPC) near full hydration. The lipid, synthesized according to the procedure of (Mason et al., 1981a, has a low degree of acyl chain migration. When MPPC is temperature-jumped (T-jumped) from the L alpha phase (T = 38 degrees C) to T = 20 degrees C or below, a subgel phase forms; this formation takes less than 1 h at a temperature below T = 12 degrees C. The subgel remains stable up to T = 29 degrees C. When MPPC is T-jumped from the L alpha phase to T = 24 degrees …
Polyunsaturated Docosahexaenoic Vs Docosapentaenoic Acid-Differences In Lipid Matrix Properties From The Loss Of One Double Bond., Nadukkudy Eldho, Scott Feller, Stephanie Tristram-Nagle, Ivan Polozov, Klaus Gawrisch
Polyunsaturated Docosahexaenoic Vs Docosapentaenoic Acid-Differences In Lipid Matrix Properties From The Loss Of One Double Bond., Nadukkudy Eldho, Scott Feller, Stephanie Tristram-Nagle, Ivan Polozov, Klaus Gawrisch
Prof. Stephanie Tristram-Nagle Ph.D.
Insufficient supply to the developing brain of docosahexaenoic acid (22:6n3, DHA), or its omega-3 fatty acid precursors, results in replacement of DHA with docosapentaenoic acid (22:5n6, DPA), an omega-6 fatty acid that is lacking a double bond near the chain's methyl end. We investigated membranes of 1-stearoyl(d(35))-2-docosahexaenoyl-sn-glycero-3-phosphocholine and 1-stearoyl(d(35))-2-docosapentaenoyl-sn-glycero-3-phosphocholine by solid-state NMR, X-ray diffraction, and molecular dynamics simulations to determine if the loss of this double bond alters membrane physical properties. The low order parameters of polyunsaturated chains and the NMR relaxation data indicate that both DHA and DPA undergo rapid conformational transitions with correlation times of the order of …