Micellization activity of the natural lipopeptide [Glu1, Asp5] surfactin-C15 in aqueous solution.
Surface tension, small angle neutron scattering (SANS), freeze-fracture transmission electron microscopy (FF-TEM), and circular dichroism (CD) have been used to study the self-aggregation properties of the natural lipopeptide [Glu(1), Asp(5)] surfactin-C15 in 0.01 M phosphate buffer solution (PBS) at pH 7.4. It has been found that the critical micelle concentration (cmc) of surfactin is 1.54 x 10(-5) M, the surface tension at the cmc (sigma(cmc)) is 27.7 mN/m, and the area per molecule at the air-water interface is 107.8 A(2). Surfactin molecules adopt a beta-sheet conformation already at low concentrations. This feature probably makes it surface-active at such low concentrations. From SANS and FF-TEM results, it is seen that surfactin exhibits a strong self-assembly ability to form sphere-like micelles and some larger aggregates even at the rare low concentration. The aggregation number of sphere-like micelles is much smaller than that for conventional surfactants of similar alkyl chain length.
State Key Laboratory of Bioreactor Engineering and Institute of Applied Chemistry, East China University of Science and Technology, Shanghai 200237, PR China.
Aihua
A
Zou
Jing
J
Liu
Vasil M
VM
Garamus
Ying
Y
Yang
Regine
R
Willumeit
Bozhong
B
Mu
D000388:Air; D002942:Circular Dichroism; D055666:Lipopeptides / Q000737:chemistry*; D008823:Micelles; D046529:Microscopy, Electron, Transmission; D010316:Particle Size; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D053838:Scattering, Small Angle; D012996:Solutions; D013500:Surface Tension; D014867:Water / Q000737:chemistry
D055666:Lipopeptides; D008823:Micelles; D010456:Peptides, Cyclic; D012996:Solutions; D014867:Water; C009365:surfactin peptide