scholarly journals The determination of the electron density profile of the human erythrocyte ghost membrane by small-angle x-ray diffraction

1977 ◽  
Vol 19 (2) ◽  
pp. 141-161 ◽  
Author(s):  
E.H. Pape ◽  
K. Klott ◽  
W. Kreutz
Keyword(s):  
Electron Density ◽  
Density Profile ◽  
Small Angle ◽  
Human Erythrocyte ◽  
Electron Density Profile ◽  
Erythrocyte Ghost ◽  
X Ray Diffraction ◽  
X Ray ◽  
Human Erythrocyte Ghost

BILMIX: a new approach to restore the size polydispersity and electron density profiles of lipid bilayers from liposomes using small-angle X-ray scattering data

2020 ◽  
Vol 53 (1) ◽  
pp. 236-243
Author(s):  
Petr V. Konarev ◽  
Maxim V. Petoukhov ◽  
Liubov A. Dadinova ◽  
Natalia V. Fedorova ◽  
Pavel E. Volynsky ◽  
...  
Keyword(s):  
Lipid Bilayer ◽  
Electron Density ◽  
Lipid Bilayers ◽  
Density Profile ◽  
Small Angle ◽  
Electron Density Profile ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Small-angle X-ray scattering (SAXS) is one of the major tools for the study of model membranes, but interpretation of the scattering data remains non-trivial. Current approaches allow the extraction of some structural parameters and the electron density profile of lipid bilayers. Here it is demonstrated that parametric modelling can be employed to determine the polydispersity of spherical or ellipsoidal vesicles and describe the electron density profile across the lipid bilayer. This approach is implemented in the computer program BILMIX. BILMIX delivers a description of the electron density of a lipid bilayer from SAXS data and simultaneously generates the corresponding size distribution of the unilamellar lipid vesicles.

scholarly journals The effect of polydispersity, shape fluctuations and curvature on small unilamellar vesicle small-angle X-ray scattering curves

2021 ◽  
Vol 54 (2) ◽  
pp. 557-568
Author(s):  
Veronica Chappa ◽  
Yuliya Smirnova ◽  
Karlo Komorowski ◽  
Marcus Müller ◽  
Tim Salditt
Keyword(s):  
Lipid Bilayer ◽  
Density Profile ◽  
Small Angle ◽  
Thermal Fluctuations ◽  
Electron Density Profile ◽  
Membrane Asymmetry ◽  
X Ray ◽  
X Ray Scattering ◽  
Vesicle Shape ◽  
Small Unilamellar Vesicles

Small unilamellar vesicles (20–100 nm diameter) are model systems for strongly curved lipid membranes, in particular for cell organelles. Routinely, small-angle X-ray scattering (SAXS) is employed to study their size and electron-density profile (EDP). Current SAXS analysis of small unilamellar vesicles (SUVs) often employs a factorization into the structure factor (vesicle shape) and the form factor (lipid bilayer electron-density profile) and invokes additional idealizations: (i) an effective polydispersity distribution of vesicle radii, (ii) a spherical vesicle shape and (iii) an approximate account of membrane asymmetry, a feature particularly relevant for strongly curved membranes. These idealizations do not account for thermal shape fluctuations and also break down for strong salt- or protein-induced deformations, as well as vesicle adhesion and fusion, which complicate the analysis of the lipid bilayer structure. Presented here are simulations of SAXS curves of SUVs with experimentally relevant size, shape and EDPs of the curved bilayer, inferred from coarse-grained simulations and elasticity considerations, to quantify the effects of size polydispersity, thermal fluctuations of the SUV shape and membrane asymmetry. It is observed that the factorization approximation of the scattering intensity holds even for small vesicle radii (∼30 nm). However, the simulations show that, for very small vesicles, a curvature-induced asymmetry arises in the EDP, with sizeable effects on the SAXS curve. It is also demonstrated that thermal fluctuations in shape and the size polydispersity have distinguishable signatures in the SAXS intensity. Polydispersity gives rise to low-q features, whereas thermal fluctuations predominantly affect the scattering at larger q, related to membrane bending rigidity. Finally, it is shown that simulation of fluctuating vesicle ensembles can be used for analysis of experimental SAXS curves.

Determination of the electron density profile and its fluctuations by broad-band microwave reflectometry in the TJ-1 tokamak

1988 ◽  
Vol 21 (9) ◽  
pp. 1384-1390 ◽  
Author(s):  
E Anabitarte ◽  
E G Bustamante ◽  
M A G Calderon ◽  
J M Senties ◽  
A P Navarro ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Profile ◽  
Broad Band ◽  
Electron Density Profile
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