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Modulation of a small two-domain lipid vesicle by linactants.

Li Z, Gorfe AA - J Phys Chem B (2014)

Bottom Line: We found that addition of a small amount of linactants (∼1%) to a two-domain vesicle leads to substantial reduction in the line tension and neck curvature at the domain boundary.Using cross-linking as a surrogate for clustering, we further show that linactant clusters substantially enhance the boundary preference and therefore the reduction in neck curvature.These results have important implications for the potential existence and physical explanations of nanosized domains in biological membranes.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston , 6431 Fannin Street, Houston, Texas 77030, United States.

ABSTRACT
Linactants, molecules that preferentially localize at the boundary of lipid membrane domains, are attracting considerable attention in recent years due to the recognition that they might regulate lipid-phase separation and thereby modulate membrane morphology. Recent studies have also shown that clustering of some line active agents enhances their ability to modulate membrane curvature. However, the molecular origin of this phenomenon, and the degree to which it impacts biological membranes, remains poorly understood. In this work, we have investigated how linactants induce shape change in multidomain small unilamallar vesicles (SUVs) using extensive dissipative particle dynamics simulations. The linactant was modeled as a two-tailed hybrid lipid with the two tails differing in preference for different lipid domains. We found that addition of a small amount of linactants (∼1%) to a two-domain vesicle leads to substantial reduction in the line tension and neck curvature at the domain boundary. Using cross-linking as a surrogate for clustering, we further show that linactant clusters substantially enhance the boundary preference and therefore the reduction in neck curvature. Moreover, on the basis of analyses of the corresponding changes in the membrane energetics, we highlight how linactants might stabilize nanoscale domains. These results have important implications for the potential existence and physical explanations of nanosized domains in biological membranes.

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Distribution of lipids and linactants. (a) Lipid distributionprofilein a vesicle with 100 monomeric hybrid lipids. (b) Lipid distributionprofile in a vesicle with 100 dimeric hybrid lipids. (c) Lipid distributionprofile in a vesicle with 100 pentameric hybrid lipids. (d) Numberof hybrid lipids at the domain boundary and the estimated line tensionfor different vesicles. The density profiles of lipid A and B werenormalized by the sum of the number of the two lipid types at each z position. The absolute number of lipids was used for linactants.
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fig6: Distribution of lipids and linactants. (a) Lipid distributionprofilein a vesicle with 100 monomeric hybrid lipids. (b) Lipid distributionprofile in a vesicle with 100 dimeric hybrid lipids. (c) Lipid distributionprofile in a vesicle with 100 pentameric hybrid lipids. (d) Numberof hybrid lipids at the domain boundary and the estimated line tensionfor different vesicles. The density profiles of lipid A and B werenormalized by the sum of the number of the two lipid types at each z position. The absolute number of lipids was used for linactants.

Mentions: Visual inspection (Figure 5b) suggests that the linactacts are distributed primarilyat the domain boundary but also across the two bulk domains. Thisis quantified in Figure 6a, which shows thaton average ∼44% (see Figure 6d) of thelinactants are located at the boundary, defined as the region between z = −2d0 and z = 4d0 based on the densityprofiles of lipids A and B. The question is what would be the impactof this boundary localization on the membrane elastic property andthe reduced curvature at the boundary? Assuming that the efficiencyof the hybrid lipids to reduce line tension is the same in planarbilayers and vesicles, one can estimate the overall reduction of theline tension (δσ) in the vesicle by the 44 (out of 100)monomeric hybrid lipids that localize at the domain boundary. Forthis, we used (i) the perimeter of the circular domain boundary, whichis estimated from the radius to be 81.0 ± 0.1d0, and (ii) the linactant efficiency obtained from planarbilayers (0.5kbT, sectionA). This yields δσ ≈ (44 × 0.5)/81 = 0.27kbT/d0. It is remarkablethat such a small change in line tension could cause global changein the vesicle shape.


Modulation of a small two-domain lipid vesicle by linactants.

Li Z, Gorfe AA - J Phys Chem B (2014)

Distribution of lipids and linactants. (a) Lipid distributionprofilein a vesicle with 100 monomeric hybrid lipids. (b) Lipid distributionprofile in a vesicle with 100 dimeric hybrid lipids. (c) Lipid distributionprofile in a vesicle with 100 pentameric hybrid lipids. (d) Numberof hybrid lipids at the domain boundary and the estimated line tensionfor different vesicles. The density profiles of lipid A and B werenormalized by the sum of the number of the two lipid types at each z position. The absolute number of lipids was used for linactants.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4120979&req=5

fig6: Distribution of lipids and linactants. (a) Lipid distributionprofilein a vesicle with 100 monomeric hybrid lipids. (b) Lipid distributionprofile in a vesicle with 100 dimeric hybrid lipids. (c) Lipid distributionprofile in a vesicle with 100 pentameric hybrid lipids. (d) Numberof hybrid lipids at the domain boundary and the estimated line tensionfor different vesicles. The density profiles of lipid A and B werenormalized by the sum of the number of the two lipid types at each z position. The absolute number of lipids was used for linactants.
Mentions: Visual inspection (Figure 5b) suggests that the linactacts are distributed primarilyat the domain boundary but also across the two bulk domains. Thisis quantified in Figure 6a, which shows thaton average ∼44% (see Figure 6d) of thelinactants are located at the boundary, defined as the region between z = −2d0 and z = 4d0 based on the densityprofiles of lipids A and B. The question is what would be the impactof this boundary localization on the membrane elastic property andthe reduced curvature at the boundary? Assuming that the efficiencyof the hybrid lipids to reduce line tension is the same in planarbilayers and vesicles, one can estimate the overall reduction of theline tension (δσ) in the vesicle by the 44 (out of 100)monomeric hybrid lipids that localize at the domain boundary. Forthis, we used (i) the perimeter of the circular domain boundary, whichis estimated from the radius to be 81.0 ± 0.1d0, and (ii) the linactant efficiency obtained from planarbilayers (0.5kbT, sectionA). This yields δσ ≈ (44 × 0.5)/81 = 0.27kbT/d0. It is remarkablethat such a small change in line tension could cause global changein the vesicle shape.

Bottom Line: We found that addition of a small amount of linactants (∼1%) to a two-domain vesicle leads to substantial reduction in the line tension and neck curvature at the domain boundary.Using cross-linking as a surrogate for clustering, we further show that linactant clusters substantially enhance the boundary preference and therefore the reduction in neck curvature.These results have important implications for the potential existence and physical explanations of nanosized domains in biological membranes.

View Article: PubMed Central - PubMed

Affiliation: Department of Integrative Biology and Pharmacology, The University of Texas Medical School at Houston , 6431 Fannin Street, Houston, Texas 77030, United States.

ABSTRACT
Linactants, molecules that preferentially localize at the boundary of lipid membrane domains, are attracting considerable attention in recent years due to the recognition that they might regulate lipid-phase separation and thereby modulate membrane morphology. Recent studies have also shown that clustering of some line active agents enhances their ability to modulate membrane curvature. However, the molecular origin of this phenomenon, and the degree to which it impacts biological membranes, remains poorly understood. In this work, we have investigated how linactants induce shape change in multidomain small unilamallar vesicles (SUVs) using extensive dissipative particle dynamics simulations. The linactant was modeled as a two-tailed hybrid lipid with the two tails differing in preference for different lipid domains. We found that addition of a small amount of linactants (∼1%) to a two-domain vesicle leads to substantial reduction in the line tension and neck curvature at the domain boundary. Using cross-linking as a surrogate for clustering, we further show that linactant clusters substantially enhance the boundary preference and therefore the reduction in neck curvature. Moreover, on the basis of analyses of the corresponding changes in the membrane energetics, we highlight how linactants might stabilize nanoscale domains. These results have important implications for the potential existence and physical explanations of nanosized domains in biological membranes.

Show MeSH
Related in: MedlinePlus