pH-Driven Self-Assembly of Acidic Microbial Glycolipids.
Microbial glycolipids are a class of well-known compounds, but their self-assembly behavior is still not well understood. While the free carboxylic acid end group makes some of them interesting stimuli-responsive compounds, the sugar hydrophilic group and the nature of the fatty acid chain make the understanding of their self-assembly behavior in water not easy and highly unpredictable. Using cryo-transmission electron microscopy (cryo-TEM) and both pH-dependent in situ and ex situ small angle X-ray scattering (SAXS), we demonstrate that the aqueous self-assembly at room temperature (RT) of a family of β-d-glucose microbial glycolipids bearing a saturated and monounsaturated C18 fatty acid chain cannot be explained on the simple basis of the well-known packing parameter. Using the "pH-jump" process, we find that the molecules bearing a monosaturated fatty acid forms vesicles below pH 6.2, as expected, but the derivative with a saturated fatty acid forms infinite bilayer sheets below pH 7.8, instead of vesicles. We show that this behavior can be explained on the different bilayer membrane elasticity as a function of temperature. Membranes are either flexible or stiff for experiments performed at a temperature respectively above or below the typical melting point, TM, of the lipidic part of each compound. Finally, we also show that the disaccharide-containing acidic cellobioselipid forms a majority of chiral fibers, instead of the expected micelles.
Sorbonne Universités, UPMC Universitè Paris 06, CNRS, Collège de France UMR 7574, Chimie de la Matière Condensée de Paris, UMR 7574, F-75005 Paris, France.
Niki
N
Baccile
Sorbonne Universités, UPMC Universitè Paris 06, CNRS, Collège de France UMR 7574, Chimie de la Matière Condensée de Paris, UMR 7574, F-75005 Paris, France.
Mohamed
M
Selmane
Sorbonne Universités, UPMC Universitè Paris 06, CNRS, Collège de France UMR 7574, Chimie de la Matière Condensée de Paris, UMR 7574, F-75005 Paris, France.
Patrick
P
Le Griel
ESRF-The European Synchrotron, High Brilliance Beamline ID02, 38043 Grenoble, France.
Sylvain
S
Prévost
SWING, Synchrotron Soleil, BP 48, 91192 Gif-sur-Yvette, France.
Javier
J
Perez
SynBioC, Department of Sustainable Organic Chemistry and Technology, Ghent University , 9000 Ghent, Belgium.
Christian V
CV
Stevens
SynBioC, Department of Sustainable Organic Chemistry and Technology, Ghent University , 9000 Ghent, Belgium.
Elisabeth
E
Delbeke
Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, 70569 Stuttgart, Germany.
Susanne
S
Zibek
Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, 70569 Stuttgart, Germany.
Michael
M
Guenther
InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, 9000, Ghent, Belgium.
Wim
W
Soetaert
InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, 9000, Ghent, Belgium.
Inge N A
IN
Van Bogaert
InBio, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University , Coupure Links 653, 9000, Ghent, Belgium.|Bio Base Europe Pilot Plant, Rodenhuizekaai 1, 9042 Ghent, Belgium.
Sophie
S
Roelants
D000143:Acids / Q000737:chemistry; D002475:Cellobiose / Q000737:chemistry; D006017:Glycolipids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008823:Micelles; D053838:Scattering, Small Angle; D014588:Ustilago / Q000737:chemistry; D014961:X-Ray Diffraction; D015003:Yeasts / Q000737:chemistry*
D000143:Acids; D006017:Glycolipids; D008823:Micelles; D002475:Cellobiose