Structure of Bolaamphiphile Sophorolipid Micelles Characterized with SAXS, SANS, and MD Simulations - Sorbonne Université Access content directly
Journal Articles Journal of Physical Chemistry B Year : 2015

Structure of Bolaamphiphile Sophorolipid Micelles Characterized with SAXS, SANS, and MD Simulations

Abstract

The micellar structure of sophorolipids, a glycolipid bolaamphiphile, is analyzed using a combination of small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and molecular dynamics (MD) simulations. Numerical modeling of SAXS curves shows that micellar morphology in the noncharged system (pH< 5) is made of prolate ellipsoids of revolution with core–shell morphology. Opposed to most surfactant systems, the hydrophilic shell has a nonhomogeneous distribution of matter: the shell thickness in the axial direction of the ellipsoid is found to be practically zero, while it measures about 12 Å at its cross-section, thus forming a “coffee bean”-like shape. The use of a contrast-matching SANS experiment shows that the hydrophobic component of sophorolipids is actually distributed in a narrow spheroidal region in the micellar core. These data seem to indicate a complex distribution of sophorolipids within the micelle, divided into at least three domains: a pure hydrophobic core, a hydrophilic shell, and a region of less defined composition in the axial direction of the ellipsoid. To account for these results, we make the hypothesis that sophorolipid molecules acquire various configurations within the micelle including bent and linear, crossing the micellar core. These results are confirmed by MD simulations which do show the presence of multiple sophorolipid configurations when passing from spherical to ellipsoidal aggregates. Finally, we also used Rb+ and Sr2+ counterions in combination with anomalous SAXS experiments to probe the distribution of the COO– group of sophorolipids upon small pH increase (5 < pH < 7), where repulsive intermicellar interactions become important. The poor ASAXS signal shows that the COO– groups are rather diffused in the broad hydrophilic shell rather than at the outer micellar/water interface.
Fichier principal
Vignette du fichier
10.1021-acs.jpcb.5b05374.pdf (1.45 Mo) Télécharger le fichier
Origin Files produced by the author(s)
Loading...

Dates and versions

hal-01281684 , version 1 (03-02-2017)

Identifiers

Cite

Sabine Manet, Anne-Sophie Cuvier, Claire Valotteau, Giulia C. Fadda, Javier Perez, et al.. Structure of Bolaamphiphile Sophorolipid Micelles Characterized with SAXS, SANS, and MD Simulations. Journal of Physical Chemistry B, 2015, 119 (41), pp.13113-13133. ⟨10.1021/acs.jpcb.5b05374⟩. ⟨hal-01281684⟩
582 View
632 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More