Interactions between pressure and ethanol on the formation of interdigitated DPPC liposomes: a study with Prodan fluorescence

Abstract

Steady-state fluorescence of 6-propionyl-2-(dimethylamino)naphthalene (Prodan) has been employed to study the interacting effects between ethanol and pressure on the formation of the fully interdigitated dipalmitoylphosphatidylcholine (DPPC). At 1 atm and 20 degrees C, a dramatic change in the emission spectrum of Prodan fluorescence is observed at about 1.1-1.3 M ethanol. The emission maximum shifts to longer wavelengths, and the intensity ratio of Prodan fluorescence at 435 nm to that at 510 nm, F435/F510, decreases abruptly with increasing ethanol content. The spectral changes are correlated to the ethanol-induced phase transition of DPPC from the noninterdigitated gel state to the fully interdigitated gel state [Rowe, E.S. (1983) Biochemistry 22, 3299-3305; Simon, S.A., & McIntosh, T.J. (1984) Biochim. Biophys. Acta 773, 169-172]. The spectral changes are attributed to the probe relocation from a less polar environment to a more polar environment due to lipid interdigitation. This relocation is either due to the bulky terminal methyl group of the lipids or due to the partition of Prodan into the bulk solution or both. The present study demonstrates that Prodan is a useful probe in monitoring the formation of the ethanol-induced fully interdigitated DPPC gel phase. Pressure is found to produce spectral changes similar to those induced by ethanol when the ethanol content amounts to 0.8-1.1 M. At lower (e.g., less than 0.4 M) and higher ethanol (e.g., greater than 2.4 M) concentrations, pressure is unable to induce such spectral changes. The critical ethanol concentrations for the formation of the fully interdigitated DPPC gel phase (Cr) have been determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermotropic Phase Behavior of Hydrogenated Soybean Phosphatidylcholine–Cholesterol Binary Liposome Membrane

“…The solvent reorientation decreases the excited state energy of Prodan molecule, which is reflected in a continuous red shift of the steady-state fluorescence spectrum. [20][21][22] Therefore, the shift of λ max or change in GP value of Prodan in HSPC liposome membrane with increasing temperature shown in Fig. 2A are attributed to the change in the polarity around Prodan molecules.…”

Effect of a Local Anesthetic Lidocaine Hydrochloride on the Bilayer Structure of Phospholipids

“…The hydrophobic fluorescent probe Prodan is extremely sensitive to solvent polarity and has been widely used to determine the physical properties of phospholipid membranes 15,[25][26][27][28][29][30][31] . In the gel phase the emission spectrum of Prodan has a maximum at 430 435 nm, which is interpreted as Prodan in hydrophobic environment, while in the liquid crystalline phase the fluorescence emission maximum is red-shifted to the region around 480 nm, suggesting a hydrophilic environment.…”

“…In the gel phase the emission spectrum of Prodan has a maximum at 430 435 nm, which is interpreted as Prodan in hydrophobic environment, while in the liquid crystalline phase the fluorescence emission maximum is red-shifted to the region around 480 nm, suggesting a hydrophilic environment. Prodan fluorescence has been also shown to respond to the formation of interdigitated gel phase in DPPC vesicles when induced by high pressure 15,25,26) and a high concentration of ethanol [26][27][28] ; the emission maximum of Prodan fluorescence is shifted dramatically to longer wavelength, that is, ca. 500 nm by pressure-induced interdigitation 15,31) and 510 520 nm by ethanol-induced interdigitation 26,28) .…”

“…Prodan fluorescence has been also shown to respond to the formation of interdigitated gel phase in DPPC vesicles when induced by high pressure 15,25,26) and a high concentration of ethanol [26][27][28] ; the emission maximum of Prodan fluorescence is shifted dramatically to longer wavelength, that is, ca. 500 nm by pressure-induced interdigitation 15,31) and 510 520 nm by ethanol-induced interdigitation 26,28) . In order to confirm the state of PC bilayer membranes in the presence of LC HCl, we measured Prodan fluorescence in various bilayer vesicles of PCs, which are shown in .…”

“…It is well known that the DPPC bilayer membrane exhibits four bilayer phases in turn, namely the lamellar crystal, lamellar gel, ripple gel and liquid crystalline phases, as temperature increases. Recent studies on the phase behavior of DPPC bilayer membrane have suggested that there exists an interdigitated gel phase, in which the hydrocarbon chains from apposing monolayers become interdigitated with the chains, induced by high concentration of alcohols 26,[36][37][38] and some local anesthetics such as tetracaine and dibucaine 32,33) as well as high pressure 24,39) . Tetracaine and dibucaine behave as a cationic surfactant because of their hydrophobic nature and have the critical micelle concentration of 128 and 79 mmol kg -1 , respectively 3,4) .…”