Reference : Nanometer scale organization of mixed surfactin/phosphatidylcholine monolayers
Scientific journals : Article
Life sciences : Agriculture & agronomy
http://hdl.handle.net/2268/36354
Nanometer scale organization of mixed surfactin/phosphatidylcholine monolayers
English
Deleu, Magali mailto [Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech >]
Paquot, Michel mailto [Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech >]
Jacques, Philippe mailto [Université de Liège > Agronomie, Bio-ingénierie et Chimie (AgroBioChem) > Bio-industries >]
Thonart, Philippe mailto [Université de Liège - ULiège > Gembloux Agro-Bio Tech > Gembloux Agro-Bio Tech - Biochimie et microbiologie industrielles >]
Adriaensen, Y. [> > > >]
Dufrene, Y. F. [> > > >]
1999
Biophysical Journal
Biophysical Society
77
4
2304-2310
Yes (verified by ORBi)
International
0006-3495
1542-0086
Bethesda
MD
[en] Mixed monolayers of the surface-active lipopeptide surfactin-C-15 and of dipalmitoyl phosphatidylcholine (DPPC) were deposited on mica and their nanometer scale organization was investigated using atomic force microscopy (AFM) and x-ray photoelectron spectroscopy (XPS). AFM topographic images revealed phase separation for mixed monolayers prepared at 0.1, 0.25, and 0.5 surfactin molar ratios. This was in agreement with the monolayer properties at the air-water interface indicating a tendency of the two compounds to form bidimensional domains in the mixed systems. The step height measured between the surfactin and the DPPC domains was 1.2 +/- 0.1 nm, pointing to a difference in molecular orientation: while DPPC had a vertical orientation, the large peptide ring of surfactin was lying on the mica surface. The N/C atom concentration ratios obtained by XPS for pure monolayers were compatible with two distinct geometric models: a random layer for surfactin and for DPPC, a layer of vertically-oriented molecules in which the polar headgroups are in contact with mica. XPS data for mixed systems were accounted for by a combination of the two pure monolayers, considering respective surface coverages that were in excellent agreement with those measured by AFM. These results illustrate the complementarity of AFM and XPS to directly probe the molecular organization of multicomponent monolayers.
http://hdl.handle.net/2268/36354
10.1016/S0006-3495(99)77069-4

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