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John F. Nagle - One of the best experts on this subject based on the ideXlab platform.
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What are the true values of the bending modulus of simple lipid bilayers
Chemistry and physics of lipids, 2014Co-Authors: John F. Nagle, Stephanie Tristram-nagle, Michael S. Jablin, Kiyotaka AkaboriAbstract:Values of the bending modulus KC are reviewed, and possible causes for the considerable differences are discussed. One possible cause is the use of glucose and sucrose in the classical micromechanical manipulation and shape analysis Methods. New data, using the more recent low angle X-Ray Method, are presented that do not support an effect of glucose or sucrose on KC. Another possible cause is using an incomplete theory to interpret the data. Adding a tilt term to the theory clearly does not affect the value obtained from the shape analysis Method. It is shown that a tilt term, using a value of the modulus Kθ indicated by simulations, theory, and estimated from order parameters obtained from NMR and from the wide angle X-Ray Method, should also not affect the value obtained using the micromechanical manipulation Method, although it does require a small correction when determining the value of the area compressibility modulus KA. It is still being studied whether including a tilt term will significantly affect the values of KC obtained using low angle X-Ray data. It remains unclear what causes the differences in the experimental values of KC for simple lipid bilayers.
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Structure of Fully Hydrated Fluid Phase Lipid Bilayers with Monounsaturated Chains
The Journal of Membrane Biology, 2006Co-Authors: Norbert Kučerka, Stephanie Tristram-nagle, John F. NagleAbstract:Quantitative structures are obtained at 30°C for the fully hydrated fluid phases of palmitoyloleoylphosphatidylcholine (POPC), with a double bond on the sn -2 hydrocarbon chain, and for dierucoylphosphatidylcholine (di22:1PC), with a double bond on each hydrocarbon chain. The form factors F ( q _ z ) for both lipids are obtained using a combination of three Methods. (1) Volumetric measurements provide F (0). (2) X-Ray scattering from extruded unilamellar vesicles provides Ι F ( q _ z )Ι for low q _ z . (3) Diffuse X-Ray scattering from oriented stacks of bilayers provides Ι F ( q _ z )Ι for high q _ z . Also, data using Method (2) are added to our recent data for dioleoylphosphatidylcholine (DOPC) using Methods (1) and (3); the new DOPC data agree very well with the recent data and with (4) our older data obtained using a liquid crystallographic X-Ray Method. We used hybrid electron density models to obtain structural results from these form factors. The result for area per lipid ( A ) for DOPC 72.4 ± 0.5 Å^2 agrees well with our earlier publications, and we find A = 69.3 ± 0.5 Å^2 for di22:1PC and A = 68.3 ± 1.5 Å^2 for POPC. We obtain the values for five different average thicknesses: hydrophobic, steric, head-head, phosphate-phosphate and Luzzati. Comparison of the results for these three lipids and for our recent dimyristoylphosphatidylcholine (DMPC) determination provides quantitative measures of the effect of unsaturation on bilayer structure. Our results suggest that lipids with one monounsaturated chain have quantitative bilayer structures closer to lipids with two monounsaturated chains than to lipids with two completely saturated chains.
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structure of fully hydrated fluid phase dmpc and dlpc lipid bilayers using x ray scattering from oriented multilamellar arrays and from unilamellar vesicles
Biophysical Journal, 2005Co-Authors: Norbert Kučerka, Yufeng Liu, Nanjun Chu, Horia I Petrache, Stephanie Tristramnagle, John F. NagleAbstract:Quantitative structures of the fully hydrated fluid phases of dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) were obtained at 30°C. Data for the relative form factors F(qz) for DMPC were obtained using a combination of four Methods. 1), Volumetric data provided F(0). 2), Diffuse X-Ray scattering from oriented stacks of bilayers provided relative form factors |F(qz)| for high qz, 0.22 < qz < 0.8 A−1. 3), X-Ray scattering from extruded unilamellar vesicles with diameter 600 A provided |F(qz)| for low qz, 0.1 < qz < 0.3 A−1. 4), Previous measurements using a liquid crystallographic X-Ray Method provided |F(2πh/D)| for h = 1 and 2 for a range of nearly fully hydrated D-spacings. The data from Method 4 overlap and validate the new unilamellar vesicles data for DMPC, so Method 4 is not required for DLPC or future studies. We used hybrid electron density models to obtain structural results from these form factors. Comparison of the model electron density profiles with that of gel phase DMPC provides areas per lipid A, 60.6 ± 0.5 A2 for DMPC and 63.2 ± 0.5 A2 for DLPC. Constraints on the model provided by volume measurements and component volumes obtained from simulations put the electron density profiles ρ(z) and the corresponding form factors F(qz) on absolute scales. Various thicknesses, such as the hydrophobic thickness and the steric thickness, are obtained and compared to literature values.
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structure of fully hydrated fluid phase dmpc and dlpc lipid bilayers using x ray scattering from oriented multilamellar arrays and from unilamellar vesicles
Biophysical Journal, 2005Co-Authors: Norbert Kučerka, Yufeng Liu, Nanjun Chu, Horia I Petrache, Stephanie Tristramnagle, John F. NagleAbstract:Quantitative structures of the fully hydrated fluid phases of dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) were obtained at 30 degrees C. Data for the relative form factors F(q(z)) for DMPC were obtained using a combination of four Methods. 1), Volumetric data provided F(0). 2), Diffuse X-Ray scattering from oriented stacks of bilayers provided relative form factors |F(q(z))| for high q(z), 0.22 < q(z) < 0.8 A(-1). 3), X-Ray scattering from extruded unilamellar vesicles with diameter 600 A provided |F(q(z))| for low q(z), 0.1 < q(z) < 0.3 A(-1). 4), Previous measurements using a liquid crystallographic X-Ray Method provided |F(2 pi h/D)| for h = 1 and 2 for a range of nearly fully hydrated D-spacings. The data from Method 4 overlap and validate the new unilamellar vesicles data for DMPC, so Method 4 is not required for DLPC or future studies. We used hybrid electron density models to obtain structural results from these form factors. Comparison of the model electron density profiles with that of gel phase DMPC provides areas per lipid A, 60.6 +/- 0.5 A(2) for DMPC and 63.2 +/- 0.5 A(2) for DLPC. Constraints on the model provided by volume measurements and component volumes obtained from simulations put the electron density profiles rho(z) and the corresponding form factors F(q(z)) on absolute scales. Various thicknesses, such as the hydrophobic thickness and the steric thickness, are obtained and compared to literature values.
Norbert Kučerka - One of the best experts on this subject based on the ideXlab platform.
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Structure of Fully Hydrated Fluid Phase Lipid Bilayers with Monounsaturated Chains
The Journal of Membrane Biology, 2006Co-Authors: Norbert Kučerka, Stephanie Tristram-nagle, John F. NagleAbstract:Quantitative structures are obtained at 30°C for the fully hydrated fluid phases of palmitoyloleoylphosphatidylcholine (POPC), with a double bond on the sn -2 hydrocarbon chain, and for dierucoylphosphatidylcholine (di22:1PC), with a double bond on each hydrocarbon chain. The form factors F ( q _ z ) for both lipids are obtained using a combination of three Methods. (1) Volumetric measurements provide F (0). (2) X-Ray scattering from extruded unilamellar vesicles provides Ι F ( q _ z )Ι for low q _ z . (3) Diffuse X-Ray scattering from oriented stacks of bilayers provides Ι F ( q _ z )Ι for high q _ z . Also, data using Method (2) are added to our recent data for dioleoylphosphatidylcholine (DOPC) using Methods (1) and (3); the new DOPC data agree very well with the recent data and with (4) our older data obtained using a liquid crystallographic X-Ray Method. We used hybrid electron density models to obtain structural results from these form factors. The result for area per lipid ( A ) for DOPC 72.4 ± 0.5 Å^2 agrees well with our earlier publications, and we find A = 69.3 ± 0.5 Å^2 for di22:1PC and A = 68.3 ± 1.5 Å^2 for POPC. We obtain the values for five different average thicknesses: hydrophobic, steric, head-head, phosphate-phosphate and Luzzati. Comparison of the results for these three lipids and for our recent dimyristoylphosphatidylcholine (DMPC) determination provides quantitative measures of the effect of unsaturation on bilayer structure. Our results suggest that lipids with one monounsaturated chain have quantitative bilayer structures closer to lipids with two monounsaturated chains than to lipids with two completely saturated chains.
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structure of fully hydrated fluid phase dmpc and dlpc lipid bilayers using x ray scattering from oriented multilamellar arrays and from unilamellar vesicles
Biophysical Journal, 2005Co-Authors: Norbert Kučerka, Yufeng Liu, Nanjun Chu, Horia I Petrache, Stephanie Tristramnagle, John F. NagleAbstract:Quantitative structures of the fully hydrated fluid phases of dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) were obtained at 30°C. Data for the relative form factors F(qz) for DMPC were obtained using a combination of four Methods. 1), Volumetric data provided F(0). 2), Diffuse X-Ray scattering from oriented stacks of bilayers provided relative form factors |F(qz)| for high qz, 0.22 < qz < 0.8 A−1. 3), X-Ray scattering from extruded unilamellar vesicles with diameter 600 A provided |F(qz)| for low qz, 0.1 < qz < 0.3 A−1. 4), Previous measurements using a liquid crystallographic X-Ray Method provided |F(2πh/D)| for h = 1 and 2 for a range of nearly fully hydrated D-spacings. The data from Method 4 overlap and validate the new unilamellar vesicles data for DMPC, so Method 4 is not required for DLPC or future studies. We used hybrid electron density models to obtain structural results from these form factors. Comparison of the model electron density profiles with that of gel phase DMPC provides areas per lipid A, 60.6 ± 0.5 A2 for DMPC and 63.2 ± 0.5 A2 for DLPC. Constraints on the model provided by volume measurements and component volumes obtained from simulations put the electron density profiles ρ(z) and the corresponding form factors F(qz) on absolute scales. Various thicknesses, such as the hydrophobic thickness and the steric thickness, are obtained and compared to literature values.
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structure of fully hydrated fluid phase dmpc and dlpc lipid bilayers using x ray scattering from oriented multilamellar arrays and from unilamellar vesicles
Biophysical Journal, 2005Co-Authors: Norbert Kučerka, Yufeng Liu, Nanjun Chu, Horia I Petrache, Stephanie Tristramnagle, John F. NagleAbstract:Quantitative structures of the fully hydrated fluid phases of dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) were obtained at 30 degrees C. Data for the relative form factors F(q(z)) for DMPC were obtained using a combination of four Methods. 1), Volumetric data provided F(0). 2), Diffuse X-Ray scattering from oriented stacks of bilayers provided relative form factors |F(q(z))| for high q(z), 0.22 < q(z) < 0.8 A(-1). 3), X-Ray scattering from extruded unilamellar vesicles with diameter 600 A provided |F(q(z))| for low q(z), 0.1 < q(z) < 0.3 A(-1). 4), Previous measurements using a liquid crystallographic X-Ray Method provided |F(2 pi h/D)| for h = 1 and 2 for a range of nearly fully hydrated D-spacings. The data from Method 4 overlap and validate the new unilamellar vesicles data for DMPC, so Method 4 is not required for DLPC or future studies. We used hybrid electron density models to obtain structural results from these form factors. Comparison of the model electron density profiles with that of gel phase DMPC provides areas per lipid A, 60.6 +/- 0.5 A(2) for DMPC and 63.2 +/- 0.5 A(2) for DLPC. Constraints on the model provided by volume measurements and component volumes obtained from simulations put the electron density profiles rho(z) and the corresponding form factors F(q(z)) on absolute scales. Various thicknesses, such as the hydrophobic thickness and the steric thickness, are obtained and compared to literature values.
Tamás Ungár - One of the best experts on this subject based on the ideXlab platform.
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characterization of nanocrystalline materials by x ray line profile analysis
Journal of Materials Science, 2007Co-Authors: Tamás UngárAbstract:X-Ray line profile analysis is shown to be a powerful tool to characterize the microstructure of nanocrystalline materials in terms of grain and subgrain size, dislocation structure and dislocation densities and planar defects, especially stacking faults and twin boundaries. It is shown that the X-Ray Method can provide valuable complementary information about the microstructure, especially when combined with transmission electron microscopy and differential scanning calorimetry.
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an x ray Method for the determination of stored energies in texture components of deformed metals application to cold worked ultra high purity iron
Acta Materialia, 2000Co-Authors: András Borbély, J.h. Driver, Tamás UngárAbstract:Abstract An X-Ray Method has been developed to evaluate the stored energy of cold work in different texture components of plastically deformed metals. The dislocation density and the outer cut-off radius of dislocations are obtained from Bragg peaks recorded from single texture components. The stored energy is approximated by the energy of dislocations, which is calculated according to the anisotropic theory of elasticity. As an example the Method is applied to the case of two major texture components developed in cold rolled ultra high purity (UHP) iron. The stored energy of the {111}〈112〉-γ fibre component of the 88% cold rolled UHP iron is about 3.6 times larger than that of the {001}〈110〉-α fibre component. The present results, of significantly higher accuracy than those of previous Methods, are in good agreement with data obtained from microhardness and recent calorimetric measurements.
K Stierstorfer - One of the best experts on this subject based on the ideXlab platform.
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density and atomic number measurements with spectral x ray attenuation Method
Journal of Applied Physics, 2003Co-Authors: Bjoern Heismann, J Leppert, K StierstorferAbstract:X-Ray attenuation measurements are widely used in medical and industrial applications. The usual results are one- to three-dimensional representations of the attenuation coefficient μ(r). In this paper, we present the ρZ projection algorithm for obtaining the density ρ(r) and atomic number Z(r) with an energy-resolving X-Ray Method. As input data the algorithm uses at least two measurements μ1,μ2,… with different spectral weightings of the source spectrum S(E) and/or detector sensitivity D(E). Analytically, ρ is a function of μ1−cμ2, c=const, and Z is a function of μ1/μ2. The full numerical treatment yields ρ(μ1,μ2) and Z(μ1,μ2) with S(E) and D(E) as commutative parametric functions. We tested the Method with dual-energy computed tomography measurements of an organic sample and a set of chemical solutions with predefined ρ and Z. The resulting images show ρ and Z as complementary information: The density ρ reflects the morphology of the objects, whereas the atomic number Z=number of electrons/atom describ...
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density and atomic number measurements with spectral x ray attenuation Method
Journal of Applied Physics, 2003Co-Authors: Bjoern Heismann, J Leppert, K StierstorferAbstract:X-Ray attenuation measurements are widely used in medical and industrial applications. The usual results are one- to three-dimensional representations of the attenuation coefficient μ(r). In this paper, we present the ρZ projection algorithm for obtaining the density ρ(r) and atomic number Z(r) with an energy-resolving X-Ray Method. As input data the algorithm uses at least two measurements μ1,μ2,… with different spectral weightings of the source spectrum S(E) and/or detector sensitivity D(E). Analytically, ρ is a function of μ1−cμ2, c=const, and Z is a function of μ1/μ2. The full numerical treatment yields ρ(μ1,μ2) and Z(μ1,μ2) with S(E) and D(E) as commutative parametric functions. We tested the Method with dual-energy computed tomography measurements of an organic sample and a set of chemical solutions with predefined ρ and Z. The resulting images show ρ and Z as complementary information: The density ρ reflects the morphology of the objects, whereas the atomic number Z=number of electrons/atom describes the material distribution. For our experimental setup we obtain an absolute precision of 0.1 for Z and 20 mg/cm3 for ρ. The ρZ projection can potentially lead to these classes of quantitative information for various scientific, industrial, and medical applications.
Nanjun Chu - One of the best experts on this subject based on the ideXlab platform.
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structure of fully hydrated fluid phase dmpc and dlpc lipid bilayers using x ray scattering from oriented multilamellar arrays and from unilamellar vesicles
Biophysical Journal, 2005Co-Authors: Norbert Kučerka, Yufeng Liu, Nanjun Chu, Horia I Petrache, Stephanie Tristramnagle, John F. NagleAbstract:Quantitative structures of the fully hydrated fluid phases of dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) were obtained at 30°C. Data for the relative form factors F(qz) for DMPC were obtained using a combination of four Methods. 1), Volumetric data provided F(0). 2), Diffuse X-Ray scattering from oriented stacks of bilayers provided relative form factors |F(qz)| for high qz, 0.22 < qz < 0.8 A−1. 3), X-Ray scattering from extruded unilamellar vesicles with diameter 600 A provided |F(qz)| for low qz, 0.1 < qz < 0.3 A−1. 4), Previous measurements using a liquid crystallographic X-Ray Method provided |F(2πh/D)| for h = 1 and 2 for a range of nearly fully hydrated D-spacings. The data from Method 4 overlap and validate the new unilamellar vesicles data for DMPC, so Method 4 is not required for DLPC or future studies. We used hybrid electron density models to obtain structural results from these form factors. Comparison of the model electron density profiles with that of gel phase DMPC provides areas per lipid A, 60.6 ± 0.5 A2 for DMPC and 63.2 ± 0.5 A2 for DLPC. Constraints on the model provided by volume measurements and component volumes obtained from simulations put the electron density profiles ρ(z) and the corresponding form factors F(qz) on absolute scales. Various thicknesses, such as the hydrophobic thickness and the steric thickness, are obtained and compared to literature values.
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structure of fully hydrated fluid phase dmpc and dlpc lipid bilayers using x ray scattering from oriented multilamellar arrays and from unilamellar vesicles
Biophysical Journal, 2005Co-Authors: Norbert Kučerka, Yufeng Liu, Nanjun Chu, Horia I Petrache, Stephanie Tristramnagle, John F. NagleAbstract:Quantitative structures of the fully hydrated fluid phases of dimyristoylphosphatidylcholine (DMPC) and dilauroylphosphatidylcholine (DLPC) were obtained at 30 degrees C. Data for the relative form factors F(q(z)) for DMPC were obtained using a combination of four Methods. 1), Volumetric data provided F(0). 2), Diffuse X-Ray scattering from oriented stacks of bilayers provided relative form factors |F(q(z))| for high q(z), 0.22 < q(z) < 0.8 A(-1). 3), X-Ray scattering from extruded unilamellar vesicles with diameter 600 A provided |F(q(z))| for low q(z), 0.1 < q(z) < 0.3 A(-1). 4), Previous measurements using a liquid crystallographic X-Ray Method provided |F(2 pi h/D)| for h = 1 and 2 for a range of nearly fully hydrated D-spacings. The data from Method 4 overlap and validate the new unilamellar vesicles data for DMPC, so Method 4 is not required for DLPC or future studies. We used hybrid electron density models to obtain structural results from these form factors. Comparison of the model electron density profiles with that of gel phase DMPC provides areas per lipid A, 60.6 +/- 0.5 A(2) for DMPC and 63.2 +/- 0.5 A(2) for DLPC. Constraints on the model provided by volume measurements and component volumes obtained from simulations put the electron density profiles rho(z) and the corresponding form factors F(q(z)) on absolute scales. Various thicknesses, such as the hydrophobic thickness and the steric thickness, are obtained and compared to literature values.
