Cooperative Tuneable Interactions between a Designed Peptide Biosurfactant and Positional Isomers of SDOBS at the Air-Water Interface

He, L. Z., Malcolm, A. S., Dimitrijev, M., Onaizi, S. A., Shen, H. H., Holt, S. A., Dexter, A. F., Thomas, R. K. and Middelberg, A. P. J. (2009) Cooperative Tuneable Interactions between a Designed Peptide Biosurfactant and Positional Isomers of SDOBS at the Air-Water Interface. Langmuir, 25 7: 4021-4026. doi:10.1021/la802825c


Author He, L. Z.
Malcolm, A. S.
Dimitrijev, M.
Onaizi, S. A.
Shen, H. H.
Holt, S. A.
Dexter, A. F.
Thomas, R. K.
Middelberg, A. P. J.
Title Cooperative Tuneable Interactions between a Designed Peptide Biosurfactant and Positional Isomers of SDOBS at the Air-Water Interface
Journal name Langmuir   Check publisher's open access policy
ISSN 0743-7463
Publication date 2009-04-07
Year available 2009
Sub-type Article (original research)
DOI 10.1021/la802825c
Open Access Status Not yet assessed
Volume 25
Issue 7
Start page 4021
End page 4026
Total pages 6
Editor David G Whitten
Place of publication Washington, D.C.
Publisher American Chemical Society
Language eng
Subject 03 Chemical Sciences
0306 Physical Chemistry (incl. Structural)
C1
Abstract Rationally designed peptide biosurfactant AM1 was mixed with sodium dodecyl benzene sulfonate (SDOBS) to self-assemble a mixed surfactant−biosurfactant layer at the air−water interface. Under optimal conditions in the presence of Zn2+, the interfacial elasticity of the mixed layer was approximately 5-fold higher than for biosurfactant alone. Two head positional isomers, SDOBS-2 and SDOBS-6, were compared for their ability to enhance interfacial film strength. SDOBS-6 forms a stronger layer with AM1 than does SDOBS-2. The highest interfacial elasticity of the AM1/SDOBS-6 layer was 640 mN m−1 whereas the maximum value for the AM1/SDOBS-2 layer was 440 mN m−1. Neutron reflection was used to investigate the structure of AM1/SDOBS films at varied bulk SDOBS concentrations. Both deuterated and nondeuterated SDOBS-2 and SDOBS-6 were used to provide contrast variation. It was shown that there is cooperative interaction between AM1 and SDOBS at low SDOBS concentration in the presence of 100 μM Zn2+, promoting AM1 adsorption at the interface to form a two-layered structure of AM1 resulting in a mechanically strong interfacial film. In the presence of EDTA, only a single AM1 layer was formed at the same SDOBS concentration, and the film did not show lateral force transmission capability. Further increasing the SDOBS concentration to a molar excess of >10× decreased the peptide population at the interface and resulted in a mechanically weak layer. Compared to SDOBS-6, SDOBS-2 depletes AM1 at a lower bulk concentration. These results demonstrate that the film strength of a self-assembled surfactant−biosurfactant mixed layer can be fine tuned by changing the isomer type and concentration of surfactant and by adding or removing metal ions.
Keyword Socdium dodecyl benzene sulfate
SDOBS
Air-water
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Thu, 03 Sep 2009, 18:20:35 EST by Mr Andrew Martlew on behalf of Aust Institute for Bioengineering & Nanotechnology