Effect of Monomer-to-Gemini Structural Change on the Self-Assembly of Peptide Surfactant

• 1、Center for Bioengeering and Biotechnology, China University of Petroleum (East China), ShanDong QingDao 266555
• 2、Center for Bioengeering and Biotechnology, China University of Petroleum (East China), Qingdao 266555

Abstract：The anionic peptide surfactant V3C that bearing hydrosulfide group was produced by introducing Cys residue into the molecule. Then by oxidation of hydrosulfide groups to form disulfide bond, a Gemini peptide surfactant V3C-CV3 was successfully synthesized. The self-assembly behaviors before and after structural change were investigated by techniques of electric conductivity measurement, fourirer transformed infrared spectroscopy, atomic force microscopy, and pH titration. V3C monomers contains pH-sensitive hydrosulfide and carboxyl groups, which can be charged via protonation/deprotonation. It shows critical aggregation concentration (CAC) of 0.16 mM and self-assembles to form membrane on the mica surface. The secondary structures contain 61.2 percent of beta-sheet. When the molecule transformed to Gemini structure of V3C-CV3, the CAC decreases greatly to be only 0.02 mM. The molecular self-assembly turns to be more orderd to form tiny fibers. Simutaneously beta-sheet content in the secondary structure increases to be about 76.9 percent. Since the pKa shows almost no variation before and after the molecular structural change, it is believed that the different self-assembly behaviors are resulted from change in configuration of each functional group while not change in charge of the molecule.

Keywords： Peptide surfactants Self-assembly Monomer Gemini