PROPERTIES OF LIPID VESICLES - FT-IR SPECTROSCOPY AND FLUORESCENCE PROBE STUDIES

The structure, conformation and dynamic properties of lipids in lamell ar phases can be studied using FT-IR and optical probe techniques, par ticularly fluorescence spectroscopy. Recent advances in the analysis o f FT-IR spectra of lipids and the use of isotopic labelling techniques have provided new insight into the conformational behaviour of the li pid chains in different lamellar phases and have made it possible to d istinguish different hydration sites in the lipid head groups. These t echniques have been extended to study lipid mixtures and to help deter mine whether microdomain formation is possible in liquid-crystalline l amellar systems. Fluorescent probe techniques are ideally suited to st udy lateral diffusion processes in lipid bilayers using either the flu orescence recovery after photobleaching (FRAP) technique or the excime r fluorescence method, the latter monitoring more local dynamic proces ses. Rotational dynamics and order of probe molecules can be determine d by time-resolved fluorescence anisotropy measurements. Both spectros copic techniques (FT-IR and fluorescence spectroscopy) are suited to g ain information on membrane heterogeneity and have improved our unders tanding of membrane behaviour.