Samples

bacteria, cells, and liposomes.

Preparation method

1mg/ml in ethanol, 30mg/ml in DMSO & DMF. Stock solution can be stored below -20℃ for several months.

Reaction Conditions

The excitation wavelength is 360 nm, and emission wavelength is 440 nm and 490 nm. [1]

Applications

Measurements of laurdan generalized polarization (GP) Laurdan is an environment-sensitive fluorescent probe, which is conventionally used for monitoring phase state of lipid membranes. [1] For liposomes, using Laurdan-containing liposomes (Laurdan/lipid molar ratio is 1:200), the vesicle suspension was added to the vesicle suspension containing 40 mM KCl, 50 μM EGTA and 10 mM Tris / HCl (pH 7.5) buffer (final lipid concentration is 50μM), and laurdan fluorescence measured before and after adding various experiments.[1] For cell membranes, the erythrocyte plasma membrane was diluted to 3 ml in 0.01 M phosphate saline buffer. Then Laurdan was added to the membrane to a final concentration of 1 μM, and incubated at 37℃ for 60 minutes to incorporate Laurdan into the red blood cell membrane. The steady-state fluorescence intensity of Laurdan was measured at 37℃ by a spectrofluorometer. The fluorescence measured in the membrane without Laurdan is always subtracted from the data. Use FLWinLab software to normalize the spectrum. [2] Laurdan fluorescence is measured (λex = 360 nm) by a Cary Eclipse spectrofluorimeter. Emission wavelengths, corresponding to the blue and red peaks of laurdan, were 440 and 490 nm. The generalized polarization (GP) was defined as GP = (I440-I490)/ (I440 + I490), where I440 and I490 are the emission intensities at 440 and 490 nm, respectively. GP can theoretically assume values from +1 (being most ordered) and – 1 (being least ordered).[1]

Laurdan is a membrane-permeable fluorescent probe that displays spectral sensitivity to the phospholipid phase of the cell membrane to which it is bound.[1] Quantitation of generalized polarization (GP) of laurdan can be used to identify phospholipid phase. When excited at 340 nm, GP values are 0.6 and -0.2 for gel phase and liquid crystalline phase, respectively. GP does not change with polar head group or pH (in the range 4-10); it changes only with phase state.

Reference:
[1]. Parasassi, T., De Stasio, G., Ravagnan, G., et al. Quantitation of lipid phases in phospholipid vesicles by the generalized polarization of Laurdan fluorescence. Biophys. J. 60(1), 179-189 (1991).