Detergent solubilization of phospholipid vesicle. Effect of electric charge

Abstract

In order to explore the effect of electric charge on detergent solubilization of phospholipid bilayers, the interaction of nine electrically charged surfactants with neutral or electrically charged liposomes has been examined. The detergents belonged to the alkyl pyridinium, alkyl trimethylammonium or alkyl sulphate families. Large unilamellar liposomes formed by egg phosphatidylcholine plus or minus stearylamine or dicetyl phosphate were used. Solubilization was assessed as a decrease in light-scattering of the liposome suspensions. The results suggest that electrostatic forces do not play a significant role in the formation of mixed micelles and that hydrophobic interactions are by far the main forces involved in solubilization. In addition, from the study of thirty different liposome-surfactant systems, we have derived a series of empirical rules that may be useful in predicting the behaviour of untested surfactants: (i) the detergent concentration producing the onset of solubilization (Don) decreases as the alkyl chain length increases; the decrease follows a semi-logarithmic pattern in the case of alkyl pyridinium compounds; (ii) for surfactants with critical micellar concentrations (cmc) less than 6 x 10(-3) M, Don. is independent of the nature of the detergent and the bilayer composition; for detergents having cmc greater than 6 x 10(-3) M, Don. increases linearly with the cmc; and (iii) Don. varies linearly with the surfactant concentration that produces maximum solubilization.

Capabilities of liposomes for topological transformation

“…Recently, many important phenomena affecting lipid bilayers, including their detergent solubilization, have been explored by using liposomes; such studies promote a better understanding of the biophysical properties of bilayer membranes and moreover will improve the handling of membrane proteins when they are isolated from or reconstructed into lipid bilayers (10)(11)(12)(13). However, studies of intermediate stages in the detergent solubilization of liposomes are only now in progress (14)(15)(16)(17), and the interaction mechanism between membranes and surfactants has remained unclear. Therefore, real-time approaches by using optical microscopy to study the dynamic behavior of liposomes are very important.…”

Quaternary Pyridinium Salts: A Review

“…The solubilization of liposomes was greatly influenced by HLB, whereas it was minorly influenced by electrostatic forces. Another study by M. Angeles Urbaneja et al had shown that the solubilization of liposomes by alkylpyridinium micelles do not largely depends upon electrostatic forces but is chiefly influenced by hydrophobic interactions 45) . Solubilization of water in organic solvents has also been achieved by pyridinium surfactants.…”

Intermediate aggregates resulting in the interaction of bile salt with liposomes studied by transmission electron microscopy and light scattering techniques

“…In accordance with the procedure described by Urbaneja et al (1990) and Ruiz et al (1994) the solubilizing interaction of SC with PC liposomes was studied through the changes in the static light-scattering 24 h after the addition of surfactant with a reading angle of 90Њ. Figure 1 shows the solubilization curve for a liposome suspension (PC concentration 5 .…”

“…It has been previously demonstrated that static light scattering (SLS) constituted a very convenient technique for the quantitative study of liposome solubilization by different surfactants (Urbaneja et al, 1990;Inoue et al, 1992;Ruiz et al, 1994). Accordingly, the solubilizing perturbation produced by the SC in PC liposomes was monitored using this technique.…”

“…0 mM. Equal volumes of the appropriate surfactant solutions were added to these liposomes and the resulting mixtures were left to equilibrate for 24 h. This time was chosen as the optimum period needed to achieve a complete equilibrium surfactant/liposome for the PC concentration used (Urbaneja et al, 1990;de la Maza & Parra, 1995). Static light-scattering measurements were made using the spectrofluorophotometer Shimadzu RF-540 equipped with a thermoregulated cell compartment at 25 ЊC with both monochromators adjusted to 500 nm.…”