Ultrafast vibrational dynamics of water confined in phospholipid reverse micelles

R Costard,N.E Levinger,C Greve,T Elsaesser,E.T.J Nibbering,M Chergui,R De Vivie-Riedle,S Cundiff,K Yamagouchi,A Taylor

doi:10.1051/epjconf/20134106003

Abstract

We study the ultrafast dynamics of OH stretching and bending vibrations of water inside dioleoylphosphatidylcholine (DOPC) reverse micelles in a wide range of hydration. A strong hydration level dependence for the spectral diffusion rates is found and explained by the distinctly different environment for single water molecules bound to the anionic phosphate group. We show that the energy relaxation pathway of the OH stretching vibration at low hydration level involves the OH bending.

Highlights

Phospholipids, building blocks of biological membranes, typically self-assemble into bilayers in aqueous solution
We recently introduced reverse micelles composed of dioleoylphosphatidylcholine (DOPC), a phospholipid with hydrophobic tails and a hydrophilic head consisting of a phosphate (PO4-) unit and a covalently linked choline group
Addition of water leads to hydration of the head groups as well as the buildup of nanoscopic water pools inside the reverse micelles

Summary

Introduction

Phospholipids, building blocks of biological membranes, typically self-assemble into bilayers in aqueous solution. Addition of water leads to hydration of the head groups as well as the buildup of nanoscopic water pools inside the reverse micelles (the water content is characterized by the parameter w0=[H2O]/[DOPC]).

Results

Conclusion