Liquid-Crystalline, Liquid-ordered, rippled and gel lipid bilayer phases as observed with nile red fluorescence
| Autor: | Goñi, Félix M., Alonso, Alicia, Gartzia-Rivero, Leire, Sot, Jesús |
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| Rok vydání: | 2022 |
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| Popis: | Póster presentado al 8th International Iberian Biophysics Congress celebrado en Bilbao los días 20 y 21 de junio de 2022. The basic matrix of cellular membranes consists of a double layer (bilayer) of phospholipids. Semisynthetic lipid bilayers are commonly in use in biophysical studies of membranes. According to temperature and composition, lipid bilayers can exist in liquid-crystalline (or liquid- disordered), liquid-ordered, rippled, and gel phases. In the present study, the hydrophobic, solvatochromic molecule Nile red has been used as a fluorescent probe to examine the physical state of bilayers of different compositions in the 15-60ºC range. Phospholipids with saturated or unsaturated acyl chains, in the presence or absence of cholesterol have been used. Nile red shows excitation maxima at 520-550 nm and emission maxima at 580-640 nm, single photon excitation not being damaging to the system. A red/orange intensity ratio (ROIR) index has been used to normalize the results. ROIR varies clearly and reproducibly with the lipid phase, increasing in the order: liquidordered > gel > rippled > liquid-crystalline. It increases with temperature and decreases with cholesterol contents in the bilayers. Nile red allows an unusually clear observation of the rippled-to-liquid crystalline phase transition in saturated phospholipids. The probe is suitable for FLIM imaging studies of isolated membrane vesicles under the confocal microscope. Rotational relaxation times have been measured for Nile red in liquid-disordered (0.71 ns), gel (1.22 ns), and liquid-ordered (1.93 ns) phases, the large value of the liquid-ordered phase being an indication of the sterol hindering probe tumbling in the hydrophobic matrix |
| Databáze: | OpenAIRE |
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