Weakly charged lamellar bilayer system: Interplay between thermal undulations and electrostatic repulsion

Berlepsch, Hans von; Vries, Renko de

doi:10.1007/pl00014594

Cited by 26 publications

(21 citation statements)

References 43 publications

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“…(43,44) To summarize, we conclude that our former results are a special case of the present analysis when the correct normalization ofp is implemented. Especially the divergence of the critical values at B 0 = 2B 1 turns out to be an artifact of the normalization ofp used in Ref.…”

Section: Appendix A: Minimal Analytic Modelsupporting

confidence: 60%

Shear-induced instabilities in layered liquids

2002

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Motivated by the experimentally observed shear-induced destabilization and reorientation of smectic A like systems, we consider an extended formulation of smectic A hydrodynamics. We include both, the smectic layering (via the layer displacement u and the layer normalp) and the director n of the underlying nematic order in our macroscopic hydrodynamic description and allow both directions to differ in non equilibrium situations. In an homeotropically aligned sample the nematic director does couple to an applied simple shear, whereas the smectic layering stays unchanged. This difference leads to a finite (but usually small) angle betweenn andp, which we find to be equivalent to an effective dilatation of the layers. This effective dilatation leads, above a certain threshold, to an undulation instability of the layers. We generalize our earlier approach [Rheol. Acta 39 (3), 15] and include the cross couplings with the velocity field and the order parameters for orientational and positional order and show how the order parameters interact with the undulation instability. We explore the influence of various material parameters on the instability. Comparing our results to recent experiments and molecular dynamic simulations, we find a good qualitative agreement.

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Section: Appendix A: Minimal Analytic Modelsupporting

confidence: 60%

Shear-induced instabilities in layered liquids

2002

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“…The dimensionless functions f e (x, Λ) and f 0 (x, Λ) refer to the even and odd mode of the undulations, respectively, and the explicit expressions are given elsewhere. 74 Following the previous studies, 61,[74][75][76] we calculated values for the difference in the bilayer area change at a given C, (∆A/A) 2 with respect to a reference value (∆A/A) 1 and the results are shown in Fig. 6.…”

Section: Resultsmentioning

confidence: 99%

Effect of interlamellar interactions on shear induced multilamellar vesicle formation

Kawabata

Bradbury

Kugizaki

et al. 2017

The Journal of Chemical Physics

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Shear-induced multilamellar vesicle (MLV) formation has been studied by coupling the small-angle neutron scattering (SANS) technique with neutron spin echo (NSE) spectroscopy. A 10% mass fraction of the nonionic surfactant pentaethylene glycol dodecyl ether (CE) in water was selected as a model system for studying weak inter-lamellar interactions. These interactions are controlled either by adding an anionic surfactant, sodium dodecyl sulfate, or an antagonistic salt, rubidium tetraphenylborate. Increasing the charge density in the bilayer induces an enhanced ordering of the lamellar structure. The charge density dependence of the membrane bending modulus was determined by NSE and showed an increasing trend with charge. This behavior is well explained by a classical theoretical model. By considering the Caillé parameters calculated from the SANS data, the layer compressibility modulus B¯ is estimated and the nature of the dominant inter-lamellar interaction is determined. Shear flow induces MLV formation around a shear rate of 10 s, when a small amount of charge is included in the membrane. The flow-induced layer undulations are in-phase between neighboring layers when the inter-lamellar interaction is sufficiently strong. Under these conditions, MLV formation can occur without significantly changing the inter-lamellar spacing. On the other hand, in the case of weak inter-lamellar interactions, the flow-induced undulations are not in-phase, and greater steric repulsion leads to an increase in the inter-lamellar spacing with shear rate. In this case, MLV formation occurs as the amplitude of the undulations gets larger and the steric interaction leads to in-phase undulations between neighboring membranes.

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“…122–126 On the other hand, it appears that the charge density on the surface of a C12E5 bilayer in water is much lower than 0.05 e / nm 2 and negative, 124, 126 even in the presence of a small amount of ionic surfactant. 127, 128 Finally, it is worth noting that the effect of NaCl on PEG/hexanol alignment is system-specific. For instance, we have not observed any significant impact of salt on alignment of ubiquitin.…”

Section: Resultsmentioning

confidence: 99%

Domain cooperativity in multidomain proteins: what can we learn from molecular alignment in anisotropic media?

2011

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Many proteins have modular design with multiple globular domains connected via flexible linkers. As a simple model of such system, we study a tandem construct consisting of two identical SH3 domains and a variable-length Gly/Ser linker. When the linker is short, this construct represents a dumbbell-shaped molecule with limited amount of domain-domain mobility. Due to its elongated shape, tandem SH3 efficiently aligns in steric alignment media. As the length of the linker increases, the two domains become effectively uncoupled and begin to behave as independent entities. Consequently, their degree of alignment drops, approaching that found in the (near-spherical) isolated SH3 domains. To model the dependence of alignment parameters on the length of the interdomain linker, we have generated in silico a series of conformational ensembles representing SH3 tandems with different linker length. These ensembles were subsequently used as input for alignment prediction software PALES. To test the accuracy of theoretical predictions, we prepared a number of tandem-SH3 samples in PEG/hexanol alignment media. These samples were used to measure backbone 1HN-15N residual dipolar couplings associated with the two globular domains within the tandem. The experimental alignment tensors determined in this fashion were compared with the results of the PALES-based simulations, broadly confirming the anticipated trends. The results of the comparison, however, fall short of quantitative agreement. In particular, it has been found that the isolated SH3 domain aligns much stronger than expected. This finding can be attributed to complex morphology of the PEG/hexanol media and/or to weak site-specific interactions between the protein and the media. In the latter case, there are strong indications that electrostatic interactions may play a role. The fact that PEG/hexanol does not behave as a simple steric media should serve as a caution for studies that use PALES as a quantitative prediction tool (especially for disordered proteins). Further progress in this area depends on our ability to accurately model the anisotropic media and its site-specific interactions with protein molecules. Once this ability is improved, it should be possible to use the alignment parameters as a measure of domain-domain cooperativity, thus identifying the situations where two domains transiently interact with each other or become coupled through a partially structured linker.

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Weakly charged lamellar bilayer system: Interplay between thermal undulations and electrostatic repulsion

Cited by 26 publications

References 43 publications

Shear-induced instabilities in layered liquids

Shear-induced instabilities in layered liquids

Effect of interlamellar interactions on shear induced multilamellar vesicle formation

Domain cooperativity in multidomain proteins: what can we learn from molecular alignment in anisotropic media?

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