scholarly journals X-ray scattering from unilamellar lipid vesicles

2005 ◽  
Vol 38 (1) ◽  
pp. 126-131 ◽  
Author(s):  
Michael R. Brzustowicz ◽  
Axel T. Brunger
Keyword(s):  
Form Factor ◽  
Lipid Bilayer ◽  
Electron Density ◽  
Lipid Vesicles ◽  
Lipid Vesicle ◽  
Asymmetric Structure ◽  
Bilayer Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

An improved small-angle X-ray scattering (SAXS) method for determining asymmetric lipid bilayer structure in unilamellar vesicles is presented. From scattering theory, analytic expressions are derived for the bilayer form factor over flat and spherical geometries, assuming the lipid bilayer electron density to be composed of a series of Gaussian shells. This is in contrast to both classic diffraction and Guinier hard-shell SAXS methods which, respectively, are capable only of ascertaining symmetric bilayer structure and limited-resolution asymmetric structure. Using model fitting and direct calculation of the form factor, using only one equation, an asymmetric electron density profile of the lipid vesicle is obtained with high accuracy, as well as the average radius. The analysis suggests that the inner leaflet of a unilamellar lipid vesicle is `rougher' than the outer one.

scholarly journals Lipid Bilayer Structure Determined by the Simultaneous Analysis of Neutron and X-Ray Scattering Data

2008 ◽  
Vol 95 (5) ◽  
pp. 2356-2367 ◽  
Author(s):  
Norbert Kučerka ◽  
John F. Nagle ◽  
Jonathan N. Sachs ◽  
Scott E. Feller ◽  
Jeremy Pencer ◽  
...  
Keyword(s):  
Lipid Bilayer ◽  
Simultaneous Analysis ◽  
Scattering Data ◽  
Bilayer Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Ray Scattering

Model-based approaches for the determination of lipid bilayer structure from small-angle neutron and X-ray scattering data

2012 ◽  
Vol 41 (10) ◽  
pp. 875-890 ◽  
Author(s):  
Frederick A. Heberle ◽  
Jianjun Pan ◽  
Robert F. Standaert ◽  
Paul Drazba ◽  
Norbert Kučerka ◽  
...  
Keyword(s):  
Lipid Bilayer ◽  
Small Angle ◽  
Scattering Data ◽  
Bilayer Structure ◽  
X Ray ◽  
Model Based ◽  
X Ray Scattering ◽  
Ray Scattering

scholarly journals Restoring structural parameters of lipid mixtures from small-angle X-ray scattering data

2021 ◽  
Vol 54 (1) ◽  
pp. 169-179 ◽  
Author(s):  
Petr V. Konarev ◽  
Andrey Yu. Gruzinov ◽  
Haydyn D. T. Mertens ◽  
Dmitri I. Svergun
Keyword(s):  
Form Factor ◽  
Small Angle ◽  
Structural Parameters ◽  
Lipid Vesicles ◽  
Delivery Systems ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Lipid Mixtures ◽  
Ray Scattering

Small-angle X-ray scattering (SAXS) is widely utilized to study soluble macromolecules, including those embedded into lipid carriers and delivery systems such as surfactant micelles, phospholipid vesicles and bilayered nanodiscs. To adequately describe the scattering from such systems, one needs to account for both the form factor (overall structure) and long-range-order Bragg reflections emerging from the organization of bilayers, which is a non-trivial task. Presently existing methods separate the analysis of lipid mixtures into distinct procedures using form-factor fitting and the fitting of the Bragg peak regions. This article describes a general approach for the computation and analysis of SAXS data from lipid mixtures over the entire angular range of an experiment. The approach allows one to restore the electron density of a lipid bilayer and simultaneously recover the corresponding size distribution and multilamellar organization of the vesicles. The method is implemented in a computer program, LIPMIX, and its performance is demonstrated on an aqueous solution of layered lipid vesicles undergoing an extrusion process. The approach is expected to be useful for the analysis of various types of lipid-based systems, e.g. for the characterization of interactions between target drug molecules and potential carrier/delivery systems.

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 Osmotic shrinkage of sterically stabilized liposomes as revealed by time-resolved small-angle X-ray scattering

2014 ◽  
Vol 47 (1) ◽  
pp. 35-40 ◽  
Author(s):  
Zoltán Varga ◽  
András Wacha ◽  
Attila Bóta
Keyword(s):  
Form Factor ◽  
Small Angle ◽  
Freeze Fracture ◽  
Initial Step ◽  
Time Resolved ◽  
X Ray ◽  
X Ray Scattering ◽  
Sterically Stabilized Liposomes ◽  
Liposome Size ◽  
Ray Scattering

Time-resolved synchrotron small-angle X-ray scattering (SAXS) was used to study the structural changes during the osmotic shrinkage of a pharmacologically relevant liposomal drug delivery system. Sterically stabilized liposomes (SSLs) with a diameter of 100 nm and composed of hydrogenated soy phosphocholine, cholesterol and distearoyl-phosphoethanolamine-PEG 2000 prepared in a salt-free buffer were mixed with a buffered 0.3 MNaCl solution using a stopped flow apparatus. The changes in the liposome size and the bilayer structure were followed by using SAXS with a time resolution of 20 ms. A linear decrease in liposome size is observed during the first ∼4 s of the osmotic shrinkage, which reveals a water permeability value of 0.215 (15) µm s−1. The change in the size of the liposomes upon the osmotic shrinkage is also confirmed by dynamic light scattering. After this initial step, broad correlation peaks appear on the SAXS curves in theqrange of the bilayer form factor, which indicates the formation of bi- or oligolamellar structures. Freeze-fracture combined with transmission electron microscopy revealed that lens-shaped liposomes are formed during the shrinkage, which account for the appearance of the quasi-Bragg peaks superimposed on the bilayer form factor. On the basis of these observations, it is proposed that the osmotic shrinkage of SSLs is a two-step process: in the initial step, the liposome shrinks in size, while the area/lipid adapts to the decreased surface area, which is then followed by the deformation of the spherical liposomes into lens-shaped vesicles.

scholarly journals Exploiting the full quantum crystallography

2018 ◽  
Vol 96 (7) ◽  
pp. 599-605 ◽  
Author(s):  
Lou Massa ◽  
Chérif F. Matta
Keyword(s):  
Quantum Mechanics ◽  
Electron Density ◽  
Mathematical Structure ◽  
Scattering Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
X Ray Scattering ◽  
Fundamental Value ◽  
Quantum Crystallography ◽  
Ray Scattering

Quantum crystallography (QCr) is a branch of crystallography aimed at obtaining the complete quantum mechanics of a crystal given its X-ray scattering data. The fundamental value of obtaining an electron density matrix that is N-representable is that it ensures consistency with an underlying properly antisymmetrized wavefunction, a requirement of quantum mechanical validity. However, X-ray crystallography has progressed in an impressive way for decades based only upon the electron density obtained from the X-ray scattering data without the imposition of the mathematical structure of quantum mechanics. Therefore, one may perhaps ask regarding N-representability “why bother?” It is the purpose of this article to answer such a question by succinctly describing the advantage that is opened by QCr.

Effect of PIP2 on Bilayer Structure and Phase Behavior of DOPC: An X-ray Scattering Study

ChemPhysChem ◽  
2011 ◽  
Vol 12 (14) ◽  
pp. 2633-2640 ◽  
Author(s):  
Sajal Kumar Ghosh ◽  
Sebastian Aeffner ◽  
Tim Salditt
Keyword(s):  
Phase Behavior ◽  
Bilayer Structure ◽  
X Ray ◽  
X Ray Scattering ◽  
Scattering Study ◽  
Ray Scattering
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