Abstract
The didodecyl ammonium amphiphile, which contains trileucine as a structural part, formed a flexible film, when its chloroform solution was spread onto a silicon-coated paper and was air-dried. On the other hand, the air-dried cast film of the tetraleucine-containing amphiphile was extremely brittle. However, the brittle film turned to a flexible film by incubation at 70℃ for 1－3 hours. Not only the thermal treatment but also hydraulic press of xerogel produced a flexible film of the tetraleucine-containing amphiphile. For example, tensile stress of the cast film of the tetraleucine-containing amphiphile increased to 6.1 MPa by 3h-incubation at 70℃, whereas the tensile stress of the pressed film increased to 3.5 MPa by hydraulic press of xerogel at 9000 N/cm2. The tri- or tetraleucine-containing amphiphiles initially formed a β-sheet structure, which stacked by a fastener-like action between the side chains of leucines within the different β-sheets (Leucine fastener). Leucine fastener brings flexibility, because a peptide-containing amphiphile except for origoleucine-containing amphiphiles did not form a flexible film. The increase of tensile stress should be also derived from Leucine fastener. Thermal treatment and the hydraulic press should promote the interlock between the side chains of leucines, and improve the mechanical strength of the films.
