Joint small-angle X-ray and neutron scattering data analysis of asymmetric lipid vesicles

Low- and high-resolution models describing the internal transbilayer structure of asymmetric lipid vesicles have been developed. These models can be used for the joint analysis of small-angle neutron and X-ray scattering data. The models describe the underlying scattering length density/electron density profiles either in terms of slabs or through the so-called scattering density profile, previously applied to symmetric lipid vesicles. Both models yield structural details of asymmetric membranes, such as the individual area per lipid, and the hydrocarbon thickness of the inner and outer bilayer leaflets. The scattering density profile model, however, comes at a cost of increased computational effort but results in greater structural resolution, showing a slightly lower packing of lipids in the outer bilayer leaflet of ∼120 nm diameter palmitoyloleoyl phosphatidylcholine (POPC) vesicles, compared to the inner leaflet. Analysis of asymmetric dipalmitoyl phosphatidylcholine/POPC vesicles did not reveal evidence of transbilayer coupling between the inner and outer leaflets at 323 K, i.e. above the melting transition temperature of the two lipids.

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Molecular Structure of Sphingomyelin in Fluid Phase Bilayers Determined by the Joint Analysis of Small-Angle Neutron and X-ray Scattering Data

The Journal of Physical Chemistry B ◽

10.1021/acs.jpcb.0c03389 ◽

2020 ◽

Vol 124 (25) ◽

pp. 5186-5200 ◽

Cited By ~ 2

Author(s):

Milka Doktorova ◽

Norbert Kučerka ◽

Jacob J. Kinnun ◽

Jianjun Pan ◽

Drew Marquardt ◽

...

Keyword(s):

Molecular Structure ◽

Small Angle ◽

Fluid Phase ◽

Scattering Data ◽

Joint Analysis ◽

X Ray ◽

X Ray Scattering ◽

Ray Scattering

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Scattering from phase-separated vesicles. I. An analytical form factor for multiple static domains

Journal of Applied Crystallography ◽

10.1107/s160057671501362x ◽

2015 ◽

Vol 48 (5) ◽

pp. 1391-1404 ◽

Cited By ~ 12

Author(s):

Frederick A. Heberle ◽

Vinicius N.P. Anghel ◽

John Katsaras

Keyword(s):

Form Factor ◽

Neutron Scattering ◽

Small Angle ◽

Small Angle Neutron Scattering ◽

Spatial Configuration ◽

Scattering Length ◽

Domain Size ◽

Lipid Vesicles ◽

Analytical Form ◽

Scattering Data

This is the first in a series of papers considering elastic scattering from laterally heterogeneous lipid vesicles containing multiple domains. Unique among biophysical tools, small-angle neutron scattering can in principle give detailed information about the size, shape and spatial arrangement of domains. A general theory for scattering from laterally heterogeneous vesicles is presented, and the analytical form factor for static domains with arbitrary spatial configuration is derived, including a simplification for uniformly sized round domains. The validity of the model, including series truncation effects, is assessed by comparison with simulated data obtained from a Monte Carlo method. Several aspects of the analytical solution for scattering intensity are discussed in the context of small-angle neutron scattering data, including the effect of varying domain size and number, as well as solvent contrast. The analysis indicates that effects of domain formation are most pronounced when the vesicle's average scattering length density matches that of the surrounding solvent.

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Small-angle scattering contrast calculator for protein and nucleic acid complexes in solution

Journal of Applied Crystallography ◽

10.1107/s0021889813025727 ◽

2013 ◽

Vol 46 (6) ◽

pp. 1889-1893 ◽

Cited By ~ 17

Author(s):

Kathryn L. Sarachan ◽

Joseph E. Curtis ◽

Susan Krueger

Keyword(s):

Nucleic Acid ◽

Small Angle ◽

Scattering Length ◽

Software Tool ◽

Scattering Data ◽

Atomistic Modeling ◽

Contrast Variation ◽

X Ray ◽

X Ray Scattering ◽

Angle Scattering

Small-angle neutron scattering (SANS) with contrast variation can provide useful information about the structure and disposition of two or more chemically distinct components within a complex. TheSASSIE Contrast Calculator(SCC) is a new software tool designed to assist in planning SANS experiments with contrast variation on protein and nucleic acid complexes. On the basis of the primary sequence and deuteration level of each protein or nucleic acid component, theSCCcalculates and plotsI(0), contrast and scattering length densities; since SANS experiments often complement small-angle X-ray scattering studies, the program provides both neutron and X-ray parameters. TheSCCis run as an integrated component ofSASSIE[Curtis, Raghunandan, Nanda & Krueger (2012).Comput. Phys. Commun.183, 382–389], a software suite for atomistic modeling of ensembles of structures consistent with scattering data.

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

Journal of Applied Crystallography ◽

10.1107/s1600576720015368 ◽

2021 ◽

Vol 54 (1) ◽

pp. 169-179 ◽

Cited By ~ 1

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.

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Global small-angle X-ray scattering data analysis for multilamellar vesicles: the evolution of the scattering density profile model

Journal of Applied Crystallography ◽

10.1107/s1600576713029798 ◽

2013 ◽

Vol 47 (1) ◽

pp. 173-180 ◽

Cited By ~ 42

Author(s):

Peter Heftberger ◽

Benjamin Kollmitzer ◽

Frederick A. Heberle ◽

Jianjun Pan ◽

Michael Rappolt ◽

...

Keyword(s):

Density Profile ◽

Small Angle ◽

Structural Information ◽

Structural Parameters ◽

Scattering Data ◽

Bilayer Thickness ◽

Multilamellar Vesicles ◽

X Ray ◽

Unsaturated Lipids ◽

Area Per Lipid

The highly successful scattering density profile (SDP) model, used to jointly analyze small-angle X-ray and neutron scattering data from unilamellar vesicles, has been adapted for use with data from fully hydrated, liquid crystalline multilamellar vesicles (MLVs). Using a genetic algorithm, this new method is capable of providing high-resolution structural information, as well as determining bilayer elastic bending fluctuations from standalone X-ray data. Structural parameters such as bilayer thickness and area per lipid were determined for a series of saturated and unsaturated lipids, as well as binary mixtures with cholesterol. The results are in good agreement with previously reported SDP data, which used both neutron and X-ray data. The inclusion of deuterated and non-deuterated MLV neutron data in the analysis improved the lipid backbone information but did not improve, within experimental error, the structural data regarding bilayer thickness and area per lipid.

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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

Journal of Applied Crystallography ◽

10.1107/s1600576719015656 ◽

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.

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A new time-of-flight small-angle scattering instrument at the Helmholtz-Zentrum Berlin: V16/VSANS

Journal of Applied Crystallography ◽

10.1107/s1600576713030227 ◽

2014 ◽

Vol 47 (1) ◽

pp. 237-244 ◽

Cited By ~ 20

Author(s):

Karsten Vogtt ◽

Miriam Siebenbürger ◽

Daniel Clemens ◽

Christian Rabe ◽

Peter Lindner ◽

...

Keyword(s):

Momentum Transfer ◽

Small Angle ◽

Soft Matter ◽

Scattering Length ◽

Time Of Flight ◽

Small Angle Scattering ◽

Neutron Guide ◽

Macromolecular Assemblies ◽

Angle Scattering ◽

The Individual

Small-angle scattering methods have become routine techniques for the structural characterization of macromolecules and macromolecular assemblies like polymers, (block) copolymers or micelles in the spatial range from a few to hundreds of nanometres. Neutrons are valuable scattering probes, because they offer freedom with respect to scattering length density contrast and isotopic labelling of samples. In order to gain maximum benefit from the allotted experiment time, the instrumental setup must be optimized in terms of statistics of scattered intensity, resolution and accessible range in momentum transferQ. The new small-angle neutron scattering instrument V16/VSANS at the Helmholtz-Zentrum in Berlin, Germany, augments neutron guide collimation and pinhole optics with time-of-flight data recording and flexible chopper configuration. Thus, the availableQrange and the respective instrumental resolution in the intermediate and high momentum transfer regions can be adjusted and balanced to the individual experimental requirements. This renders V16/VSANS a flexible and versatile instrument for soft-matter research.

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