Mixed monolayers of 1,2-diphytanoyl-sn-glycero-3-phosphocholine and a synthetic ion channel-forming peptide oligomer M2: An isotherm and BAM study

COLL 103

Kun Fang1, Jun Zhang1, Randolph S. Duran1, Frank J. Raucci2, Joanna R. Long3, Ingo Köper4, Stefan Schiller4, and Wolfgang Knoll4. (1) Butler Polymer Laboratory, Department of Chemistry, University of Florida, Gainesville, FL 36211, (2) Biochemistry and Molecular Biology and McKnight Brain Institute, University of Florida, Gainesville, FL 36211, (3) Biochemistry and Melecular Biology, University of Florida, Gainesville, FL 36211, (4) Max-Planck-Institut für Polymerforschung, Ackermannweg 10, 55128 Mainz, Germany
Synthetic peptides and lipids are widely used to mimic functional biomembranes. The mixed monolayers of 1,2-diphytanoyl-sn-glycero-3-phosphocholine (DPhPC) and M2 (a synthetic ion channel-forming peptide oligomer) were examined at the air/water interface. While varying the mixed ratio of the two components, the resulting monolayers were studied through surface pressure-area isotherms and Brewster Angle Microscopy (BAM). Both isotherm and BAM results showed that pure DPhPC monolayer exists in a uniform phase, while the M2 monolayer undergoes two phase transitions upon an increase in surface pressure. However, such phase transitions disappeared when DPhPC was incorporated, especially at higher mixed ratios of DPhPC. From these isotherms, the excess surface areas of mixing at different surface pressures were typically found to be positive. The unusual non-ideal mixing behavior of this system will be discussed.