Laurdan-Labeled LUVs Membrane Packing

The stock suspension of 100 μM LUV₁₀₀ was labeled with 0.2 μM concentration of 2-dimethylamino-6-lauroyl naphthalene (Laurdan, Molecular Probes, dissolved in dimethylsulfoxide, DMSO) at 37 °C for 60 min, the final ratio of Laurdan per lipid was 1 : 500. Final concentration of DMSO was 0.2% in all samples. The LUV suspension was split to individual aliquots of 0.1 mL. To study the possible shift in packing of the lipids in membranes with two different compositions (DOPE : DOPG and DOPG : DOPE, 2 : 1, w/w), we measured the generalized polarization (GP) of Laurdan-labeled LUVs under stable temperature 27 °C using FluoroMax-3 spectrofluorometer (Jobin Yvon, Horiba). Fluorescence spectra were measured from 400 to 600 nm (after excitation at 365 nm), with 4 nm bandpass. GP values were calculated according to Parasassi et al. (1990).^{28 (link)}