Formation mechanism of self-assembled unilamellar vesiclesSpecial issue on Neutron Scattering in Canada

2010 ◽  
Vol 88 (10) ◽  
pp. 735-740 ◽  
Author(s):  
Mu-Ping Nieh ◽  
Norbert Kučerka ◽  
John Katsaras
Keyword(s):  
Neutron Scattering ◽  
Hydrocarbon Chain ◽  
Lipid Concentration ◽  
Uniform Size ◽  
Lipid Mixtures ◽  
Hydrocarbon Chain Length ◽  
Membrane Rigidity ◽  
Self Assembled ◽  
Best Fit ◽  
Sans Data

Uniform size self-assembled unilamellar vesicles (ULVs) can be produced from mixtures of weakly charged short- and long-chain phospholipids. These lipid mixtures self-assemble into bilayered micelles (so-called bicelles), and a bicelle to ULV transition has been previously reported. Here, we discuss the effect of various parameters (i.e., lipid concentration, charge density, membrane rigidity, lipid composition, and lipid hydrocarbon chain length) on ULV radius as determined by small angle neutron scattering (SANS). SANS data were best fit using a core-shell disk and a spherical-shell model to obtain the size of bicelles and ULVs, respectively. From the present experiments we conclude that a previously proposed mechanism of ULV formation, where bicelles coalesce into large precursor and self-fold into ULVs, is able to explain the present SANS data.

scholarly journals Structure and Interdigitation of Chain-Asymmetric Phosphatidylcholines and Milk Sphingomyelin in the Fluid Phase

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1441
Author(s):  
Moritz P. K. Frewein ◽  
Milka Doktorova ◽  
Frederick A. Heberle ◽  
Haden L. Scott ◽  
Enrico F. Semeraro ◽  
...  
Keyword(s):  
Chain Length ◽  
Hydration Shell ◽  
Fluid Phase ◽  
Hydrocarbon Chain ◽  
Specific Model ◽  
Glycerol Backbone ◽  
Membrane Composition ◽  
Membrane Structures ◽  
Hydrocarbon Chain Length ◽  
Dynamics Simulations

We addressed the frequent occurrence of mixed-chain lipids in biological membranes and their impact on membrane structure by studying several chain-asymmetric phosphatidylcholines and the highly asymmetric milk sphingomyelin. Specifically, we report trans-membrane structures of the corresponding fluid lamellar phases using small-angle X-ray and neutron scattering, which were jointly analyzed in terms of a membrane composition-specific model, including a headgroup hydration shell. Focusing on terminal methyl groups at the bilayer center, we found a linear relation between hydrocarbon chain length mismatch and the methyl-overlap for phosphatidylcholines, and a non-negligible impact of the glycerol backbone-tilting, letting the sn1-chain penetrate deeper into the opposing leaflet by half a CH2 group. That is, penetration-depth differences due to the ester-linked hydrocarbons at the glycerol backbone, previously reported for gel phase structures, also extend to the more relevant physiological fluid phase, but are significantly reduced. Moreover, milk sphingomyelin was found to follow the same linear relationship suggesting a similar tilt of the sphingosine backbone. Complementarily performed molecular dynamics simulations revealed that there is always a part of the lipid tails bending back, even if there is a high interdigitation with the opposing chains. The extent of this back-bending was similar to that in chain symmetric bilayers. For both cases of adaptation to chain length mismatch, chain-asymmetry has a large impact on hydrocarbon chain ordering, inducing disorder in the longer of the two hydrocarbons.

scholarly journals Effect of Hydrocarbon Chain Length of Amphiphilic Ruthenium Dyes on Solid-State Dye-Sensitized Photovoltaics

Nano Letters ◽  
2005 ◽  
Vol 5 (7) ◽  
pp. 1315-1320 ◽  
Author(s):  
Lukas Schmidt-Mende ◽  
Jessica E. Kroeze ◽  
James R. Durrant ◽  
Md. K. Nazeeruddin ◽  
Michael Grätzel
Keyword(s):  
Solid State ◽  
Chain Length ◽  
Hydrocarbon Chain ◽  
Dye Sensitized ◽  
Hydrocarbon Chain Length ◽  
Ruthenium Dyes

In-situsmall-angle neutron scattering study of pore filling and pore emptying in ordered mesoporous silica

2009 ◽  
Vol 43 (1) ◽  
pp. 1-7 ◽  
Author(s):  
M. Erko ◽  
D. Wallacher ◽  
A. Brandt ◽  
O. Paris
Keyword(s):  
Neutron Scattering ◽  
Capillary Condensation ◽  
Pore Filling ◽  
Perfect Agreement ◽  
Filling Fraction ◽  
Ordered Mesoporous ◽  
Scattering Study ◽  
Neutron Scattering Study ◽  
Sans Data

The capillary condensation and capillary emptying of water and perfluoropentane in ordered mesoporous SBA-15 silica is studied byin-situsmall-angle neutron scattering (SANS). The SANS data can be perfectly described by a simple analytical model for spatially random pore filling (Laue scattering) for the entire range of pore-filling fractions. From this it is concluded that recently proposed pore correlations due to elastic interactions between neighbouring pores upon capillary condensation do not play a role in this system. The pores fill randomly according to their size distribution, in perfect agreement with the classical Kelvin equation. The relation between the overall pore-filling fraction as determined from the volumetric sorption isotherm, and the fraction of completely filled pores as obtained from the fit of the SANS data, allows conclusions to be drawn about the thermodynamic metastability of the adsorption process.

scholarly journals Quantitative 3D determination of self-assembled structures on nanoparticles using small angle neutron scattering

2018 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhi Luo ◽  
Domenico Marson ◽  
Quy K. Ong ◽  
Anna Loiudice ◽  
Joachim Kohlbrecher ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Self Assembled

scholarly journals Crystal Memory near Discontinuous Triacylglycerol Phase Transitions: Models, Metastable Regimes, and Critical Points

Molecules ◽  
2020 ◽  
Vol 25 (23) ◽  
pp. 5631
Author(s):  
David A. Pink ◽  
Marjorie Ladd-Parada ◽  
Alejandro G. Marangoni ◽  
Gianfranco Mazzanti
Keyword(s):  
Phase Transition ◽  
Critical Point ◽  
Single Phase ◽  
Hydrocarbon Chain ◽  
Temperature Data ◽  
Recent Time ◽  
Recent Experimental Data ◽  
Hydrocarbon Chain Length ◽  
Discontinuous Phase ◽  
Solid Liquid

It is proposed that “crystal memory”, observed in a discontinuous solid-liquid phase transition of saturated triacylglycerol (TAG) molecules, is due to the coexistence of solid TAG crystalline phases and a liquid TAG phase, in a superheated metastable regime. Such a coexistence has been detected. Solid crystals can act as heterogeneous nuclei onto which molecules can condense as the temperature is lowered. We outlined a mathematical model, with a single phase transition, that shows how the time-temperature observations can be explained, makes predictions, and relates them to recent experimental data. A modified Vogel-Fulcher-Tammann (VFT) equation is used to predict time-temperature relations for the observation of “crystal memory” and to show boundaries beyond which “crystal memory” is not observed. A plot of the lifetime of a metastable state versus temperature, using the modified VFT equation, agrees with recent time-temperature data. The model can be falsified through its predictions: the model possesses a critical point and we outline a procedure describing how it could be observed by changing the hydrocarbon chain length. We make predictions about how thermodynamic functions will change as the critical point is reached and as the system enters a crossover regime. The model predicts that the phenomenon of “crystal memory” will not be observed unless the system is cooled from a superheated metastable regime associated with a discontinuous phase transition.

Sign in / Sign up

Export Citation Format

Share Document