1. Biochim Biophys Acta. 2013 Feb;1828(2):801-15. doi: 10.1016/j.bbamem.2012.11.007.
Epub 2012 Nov 14.

Effects of surfactin on membrane models displaying lipid phase separation.

Deleu M, Lorent J, Lins L, Brasseur R, Braun N, El Kirat K, Nylander T, Dufrêne
YF, Mingeot-Leclercq MP.

Université de Liège, Gembloux Agro-Bio Tech, Unité de Chimie Biologique
Industrielle, Passage des Déportés, 2, B-5030 Gembloux, Belgium. Electronic
address: magali.deleu@ulg.ac.be.

Surfactin, a bacterial amphiphilic lipopeptide is attracting more and more
attention in view of its bioactive properties which are in relation with its
ability to interact with lipids of biological membranes. In this work, we
investigated the effect of surfactin on membrane structure using model of
membranes, vesicles as well as supported bilayers, presenting coexistence of
fluid-disordered (DOPC) and gel (DPPC) phases. A range of complementary methods
was used including AFM, ellipsometry, dynamic light scattering, fluorescence
measurements of Laurdan, DPH, calcein release, and octadecylrhodamine B
dequenching. Our findings demonstrated that surfactin concentration is critical
for its effect on the membrane. The results suggest that the presence of rigid
domains can play an essential role in the first step of surfactin insertion and
that surfactin interacts both with the membrane polar heads and the acyl chain
region. A mechanism for the surfactin lipid membrane interaction, consisting of
three sequential structural and morphological changes, is proposed. At
concentrations below the CMC, surfactin inserted at the boundary between gel and 
fluid lipid domains, inhibited phase separation and stiffened the bilayer without
global morphological change of liposomes. At concentrations close to CMC,
surfactin solubilized the fluid phospholipid phase and increased order in the
remainder of the lipid bilayer. At higher surfactin concentrations, both the
fluid and the rigid bilayer structures were dissolved into mixed micelles and
other structures presenting a wide size distribution.

Copyright © 2012 Elsevier B.V. All rights reserved.

PMID: 23159483  [PubMed - in process]