Abstract

Three-pulse photon-echo peak-shift (3PEPS) experiments were performed to explore structural relaxations relevant to solvation of a cyanine dye non-covalently anchored to aqueous interfaces of unilamellar phospholipid vesicles. The influence of the lipid polymorphism is studied through the temperature-dependence of the 3PEPS decay. As opposed to the main order/disorder phase transition connected with packing phenomena in the hydrophobic membrane core, the rippled-to-gel pre-transition strongly affects the solvation response on time scales below 2 ps. This finding indicates that the pre-transition is connected with structural modifications of the hydration shell surrounding the polar head groups and is consistent with a dehydration of the interface.

© 2002 Optical Society of America