Hydration and Mobility in Lipid Bilayers Probed by Time-Dependent Fluorescence Shift

Abstract

Biological membranes as an indispensable part of living organisms are permanently surrounded by the molecules of water. The presence of water is essential for maintaining their structure and functionality. Therefore, lipid bilayer hydration, mobility of the hydrated lipids, and their changes upon perturbations are appealing characteristics in the lipid membrane research. Time-dependent fluorescent shift (TDFS) measurements enable probing these properties in biologically relevant fully hydrated liquid crystalline lipid bilayers with a simple instrumentation and easy data treatment. Since the native lipid molecules do not fluoresce naturally, the extrinsic probing with a suitable fluorescent dye is necessary. There are a number of fluorescent membrane polarity probes designed for this purpose with different spectral properties and locations within the lipid bilayer. The basics of the technique are explained together with some useful additional considerations. The convenience of the TDFS method is demonstrated with examples from recent research on the study of the interactions of ions with lipid bilayers, and the monitoring of mobility and hydration changes along the bilayer normal upon addition of the oxidized phospholipids.