Fluctuation dynamics of bilayer vesicles with intermonolayer sliding: Experiment and theory

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The presence of coupled modes of membrane motion in closed shells is extensively predicted by theory. The bilayer structure inherent to lipid vesicles is suitable to support hybrid modes of ctirvature motion coupling membrane bending with the local reorganization of the bilayer material through relaxation of the dilatational stresses. Previous experiments evidenced the existence of such hybrid modes facilitating membrane bending at high curvatures in lipid vesicles [Rodriguez-Garcia, R., Arriaga, L.R., Mell, M., Moleiro, L.H., Lopez-Montero, I., Monroy, F., 2009. Phys. Rev. Lett. 102, 1282011. For lipid bilayers that are able to undergo intermonolayer sliding, the experimental fluctuation spectra are found compatible with a bimodal schema. The usual tension/bending fluctuations couple with the hybrid modes in a mechanical interplay, which becomes progressively efficient with increasing vesicle radius, to saturate at infinity radius into the behavior expected for a flat membrane. Grounded on the theory of closed shells, we propose an approximated expression of the bimodal spectrum, which predicts the observed dependencies on the vesicle radius. The dynamical features obtained from the autocorrelation functions of the vesicle fluctuations are found in quantitative agreement with the proposed theory. (C) 2014 Elsevier Ireland Ltd. All rights reserved.
This work was funded by MICINN under grants FIS2012-35723, FIS2009-14650-C02-01, Consolider-Ingenio 2010 en "Nanociencia Molecular" (CSD2007-0010), S2013/MIT-2807 (NanoBIOSOMA) and TS2009MAT-1507T (NOBIMAT) from CAM. M. Mell was supported by FPU Program (MEC) and L.H. Moleiro by CSD2007-0010. I. López-Montero thanks support from NOBIMAT (CAM). We gratefully acknowledge ILL Soft Matter Partnership Lab
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