Laurdan properties in glycosphingolipid-phospholipid mixtures: a comparative fluorescence and calorimetric study

LUIS A. BAGATOLLI; BRUNO MAGGIO; FELIPE AGUILAR; CARLOS P. SOTOMAYOR; GERARDO D. FIDELIO

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1997 vol. 1325 p. 80 - 80

0005-2736

aurdan (6-dodecanoyl-2-dimethylamine-naphthalene) is a fluorescent membrane probe of recent characterization. It was shown that this probe discriminates between phase transitions, phase fluctuations and the coexistence of phase domains in phospholipid multilamellar aggregates. We measured the excitation and emission generalized polarization (GP(ex) and GP(em)) of Laurdan in aggregates of complex glycosphingolipids in their pure form and in mixtures with dipalmitoylphosphatidylcholine (DPPC). Our results show that Laurdan detects the broad main phase transition temperature of the neutral ceramide-tetrasaccharide Gg(4)Cer (asialo-G(M1)) and shows a value of GP(ex) in between that of DPPC and that of ganglioside G(M1). In contrast, Laurdan was unable to detect the thermotropic phase transition of G(M1). The probe also appears to be unable to detect phase coexistence in both types of pure glycolipid aggregates. Deconvolution of the excess heat capacity vs. temperature curves of pure Gg(4)