Determination of mosaicity in oriented stacks of lipid bilayers

Nagle, John F.; Akabori, Kiyotaka; Treece, Bradley W.; Tristram-Nagle, Stephanie

doi:10.1039/c5sm02336j

Cited by 16 publications

(14 citation statements)

References 25 publications

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“…The lobes of diffuse scattering result from fluctuational disorder that occurs spontaneously in fully hydrated, oriented bilayers. Analysis of the weak arcs emanating from the diffuse, white lobes [43] indicates a small mosaic spread (i.e., an excellent bilayer alignment) with mosaic spread <1 degree. Although visual comparison shows only small differences between the lobes of diffuse scattering data in Fig.…”

Section: Resultsmentioning

confidence: 99%

HIV-1 matrix-31 membrane binding peptide interacts differently with membranes containing PS vs. PI(4,5)P2

O'neil

Andenoro

Pagano

et al. 2016

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Efficient assembly of HIV-1 at the plasma membrane (PM) of the T-cell specifically requires PI(4,5)P2. It was previously shown that a highly basic region (HBR) of the matrix protein (MA) on the Gag precursor polyprotein Pr55Gag is required for membrane association. MA is N-terminally myristoylated, which enhances its affinity to membranes. In this work we used X-ray scattering and neutron reflectivity to determine how the physical properties and structure of lipid bilayers respond to the addition of binding domain peptides, either in the myristoylated form (MA31myr) or without the myristoyl group (MA31). Neutron reflectivity measurements showed the peptides predominantly located in the hydrocarbon interior. Diffuse X-ray scattering showed differences in membrane properties upon addition of peptides and the direction of the changes depended on lipid composition. The PI(4,5)P2-containing bilayers softened, thinned and became less ordered as peptide concentration increased. In contrast, POPS-containing bilayers with equivalent net charge first stiffened, thickened and became more ordered with increasing peptide concentration. As softening the host cell’s PM upon contact with the protein lowers the free energy for membrane restructuring, thereby potentially facilitating budding of viral particles, our results suggest that the role of PI(4,5)P2 in viral assembly goes beyond specific stereochemical membrane binding. These studies reinforce the importance of lipids in virology.

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Section: Resultsmentioning

confidence: 99%

HIV-1 matrix-31 membrane binding peptide interacts differently with membranes containing PS vs. PI(4,5)P2

O'neil

Andenoro

Pagano

et al. 2016

Biochimica et Biophysica Acta (BBA) - Biomembranes

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“…This method takes advantage of the fact that oriented samples are never perfect, but have mosaicity consisting of many misoriented microdomains within the footprint of the beam. The angular distribution of this apparently continuous mosaicity is closer to Lorentzian than to Gaussian, 22 so an exposure at a fixed substrate angle  F not equal to a Bragg angle  h still shows peaks for the h th order with the relative intensity decreasing gradually for those peaks with Bragg angles further from the fixed exposure angle, i.e., for larger | F - h |. The new method sets the fixed angle midway between the Bragg angle of two orders,  F = ½ ( h1 +  h2 ).…”

Section: B Data Acquisitionmentioning

confidence: 87%

“…On the other hand, diffraction from mis-oriented domains is cut off by the rotating substrate when the domains are mis-oriented by more than the Bragg angle  h ≈ 0.5h degrees in our setup. The width of the mosaic distribution for our oriented samples is difficult to obtain accurately and is subject to some ambiguity due to long tails in the mosaic distribution, 22 but supposing that it could be as large as 0.5 degrees for this gel phase sample would substantially reduce the intensity I h=1 but would hardly reduce I h for h≥3. We did observe some reduction in the ratio of I 1 /I 3 by comparison with intensity ratios obtained from multilamellar vesicles (MLV) in capillaries which do not suffer from this cutoff artifact.…”

Section: Repeat Spacings and Peak Intensitiesmentioning

confidence: 99%

Structure of gel phase DPPC determined by X-ray diffraction

Nagle

Cognet

Dupuy

et al. 2019

Chemistry and Physics of Lipids

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High resolution low angle x-ray data are reported for the gel phase of DPPC lipid bilayers, extending the previous q range of 1.0 Å -1 to 1.3 Å -1 , and employing a new technique to obtain more accurate intensities and form factors |F(q)| for the highest orders of diffraction. Combined with previous wide angle x-ray and volumetric data, a space filling model is employed to obtain gel phase structure at a mesoscopic level. A new conclusion from this analysis is that the hydrocarbon chains from opposing monolayers are mini-interdigitated; this would help explain the previously well-established result that the opposing monolayers are strongly coupled with respect to their chain tilt directions.Even more detailed structural features are described that have not been obtained from experiment but that could, in principle, be obtained from simulations that would first be validated by agreement with the wide angle and the new low angle |F(q)| x-ray data.

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“…After addition of Ca 2+ the compacted phase had a mosaicity of 0.26°. Both values show a reasonable orientation for hydrated samples [ 45 ].…”

Section: Resultsmentioning

confidence: 99%

Cooling induces phase separation in membranes derived from isolated CNS myelin

Pusterla

Schneck

Funari³

et al. 2017

PLoS ONE

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Purified myelin membranes (PMMs) are the starting material for biochemical analyses such as the isolation of detergent-insoluble glycosphingolipid-rich domains (DIGs), which are believed to be representatives of functional lipid rafts. The normal DIGs isolation protocol involves the extraction of lipids under moderate cooling. Here, we thus address the influence of cooling on the structure of PMMs and its sub-fractions. Thermodynamic and structural aspects of periodic, multilamellar PMMs are examined between 4°C and 45°C and in various biologically relevant aqueous solutions. The phase behavior is investigated by small-angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC). Complementary neutron diffraction (ND) experiments with solid-supported myelin multilayers confirm that the phase behavior is unaffected by planar confinement. SAXS and ND consistently show that multilamellar PMMs in pure water become heterogeneous when cooled by more than 10–15°C below physiological temperature, as during the DIGs isolation procedure. The heterogeneous state of PMMs is stabilized in physiological solution, where phase coexistence persists up to near the physiological temperature. This result supports the general view that membranes under physiological conditions are close to critical points for phase separation. In presence of elevated Ca2+ concentrations (> 10 mM), phase coexistence is found even far above physiological temperatures. The relative fractions of the two phases, and thus presumably also their compositions, are found to vary with temperature. Depending on the conditions, an “expanded” phase with larger lamellar period or a “compacted” phase with smaller lamellar period coexists with the native phase. Both expanded and compacted periods are also observed in DIGs under the respective conditions. The observed subtle temperature-dependence of the phase behavior of PMMs suggests that the composition of DIGs is sensitive to the details of the isolation protocol.

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Determination of mosaicity in oriented stacks of lipid bilayers

Cited by 16 publications

References 25 publications

HIV-1 matrix-31 membrane binding peptide interacts differently with membranes containing PS vs. PI(4,5)P2

HIV-1 matrix-31 membrane binding peptide interacts differently with membranes containing PS vs. PI(4,5)P2

Structure of gel phase DPPC determined by X-ray diffraction

Cooling induces phase separation in membranes derived from isolated CNS myelin

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