Effect of ethanol-induced lipid interdigitation on the membrane solubility of Prodan, Acdan, and Laurdan

Abstract

The effect of ethanol-induced lipid interdigitation on the partition coefficient (Kp) of 6-propionyl-2-(dimethylamino)naphthalene (Prodan) and its two derivatives, 6-acetyl-2-(dimethylamino)naphthalene (Acdan) and 6-lauroyl-2-(dimethylamino)naphthalene (Laurdan), in L-alpha-dipalmitoylphosphatidylcholine (DPPC) vesicles has been examined by a precipitation method over the ethanol concentration range of 0-1.8 M. At 20 degrees C and in the absence of ethanol, the Kp values for Acdan, Prodan, and Laurdan are 2.0 x 10(3), 2.8 x 10(4), and 4.7 x 10(6), respectively. This result suggests that the Kp of Prodan and its derivatives is not simply a linear function of the polymethylene units. As DPPC undergoes the ethanol-induced phase transition from the noninterdigitated to the fully interdigitated gel state, Kp for Prodan and Acdan decreases by a factor of 5 and 2, respectively, whereas Kp for Laurdan exhibits no detectable changes with ethanol. The differences in Kp are in parallel with the differences in the fluorescence emission spectra of these probes over the ethanol concentration range examined. Previous fluorescence and infrared data indicated that membrane perturbation caused by the probes increases in the order: Laurdan > Prodan > Acdan. Thus, the degree of membrane perturbation also seems to be in parallel with Kp. Among these three probes, Prodan fluorescence reflects most correctly the ethanol-induced lipid interdigitation. In conclusion, the partitioning of small solutes in lipid membranes is significantly reduced by ethanol-induced lipid interdigitation, probably as a result of an increased membrane surface density due to the increased intramolecular lipid acyl chain ordering and a tighter overall intermolecular packing.

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

“…At a LC HCl concentration above 0.37 M, the emission spectrum of Prodan in DPPC vesicle displays a dominant peak at 518 nm, which is approaching to the emission maximum in water, i.e., 528 nm 15) . Similar phenomenon has been observed in the case of ethanol-induced interdigitation 28) . So far, some local anesthetics such as tetracaine and dibucaine are known to induce the interdigitated gel phase in the DPPC bilayer membrane 32,33) .…”

“…The value of emission maximum in the DOPC and EPC bilayers was 516 nm, which means less hydrophilic environment than that in DPPC bilayer (at 25 ) in the presence of 0.74 M LC HCl. Partition coefficient of Prodan into the interdigitated gel phase of DPPC bilayer is known to be significantly small 28) , compared with that in other phases of lipid bilayers. This reduced partition coefficient of Prodan into the interdigitated gel phase plus the replacement of Prodan by LC HCl becoming high concentration are probably responsible for the significant redshift of emission maximum of Prodan as is seen in .…”

“…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 .…”