UC Irvine

There are several commonly used approaches for the study of membrane properties of live cells based on fluorescence probes. In one approach, lipids with specific fluorescent markers are incorporated in the cell membranes. The advantage of this approach is that it is possible to study the membrane distribution of specific lipids. However, when the aim of the study is to detect membrane microdomains independently of their lipid composition, it is more useful to use a single probe that can report on the specific properties of the membrane microdomains, independently of the probe segregation in one specific domain and location in the cell. One fluorescent probe that has been successfully used for this purpose is the lipophilic probe Laurdan (2-dimethylamino-6-lauroylnaphthalene), originally synthesized by Weber and Farris.1 Different membrane environments produce marked changes both in the spectrum and in the fluorescence lifetime of Laurdan. The sensitivity of the emission spectrum of Laurdan to the environment originates from the specific molecular structure of Laurdan in which the excited-state dipole is substantially different from the ground-state dipole (Figure 13.1).