Early and delayed stages in the solubilization of purple membrane by a polyoxyethylenic surfactant

Viguera, Ana Rosa; González-Mañas, Juan Manuel; Taneva, Stefka G.; Goñi, Félix M.

doi:10.1016/0005-2736(94)90297-6

Cited by 11 publications

(5 citation statements)

References 19 publications

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“…Our results support this hypothesis, underlining in addition the difficulty for detergents to become inserted in ordered domains. A similar situation was found for the solubilization of the tightly packed purple membrane patches in Halobacterium membranes (42) and for the case of dimyristoyl PC/Ch bilayers in the liquid-ordered state (11). Our observation of an increased solubilization at temperatures above T m of the phospholipids (Fig.…”

Section: Detergent Resistancesupporting

confidence: 86%

Detergent-Resistant, Ceramide-Enriched Domains in Sphingomyelin/Ceramide Bilayers

Sot

Bagatolli

Goñi

et al. 2006

Biophysical Journal

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144

128

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When cell membranes are treated with Triton X-100 or other detergents at 4 degrees C, a nonsolubilized fraction can often be recovered, the "detergent-resistant membranes", that is not found when detergent treatment takes place at 37 degrees C. Detergent-resistant membranes may be related in some cases to membrane "rafts". However, several basic aspects of the formation of detergent-resistant membranes are poorly understood. To answer some of the relevant questions, a simple bilayer composition that would mimic detergent-resistant membranes was required. The screening of multiple lipid compositions has shown that the binary mixture egg sphingomyelin/egg ceramide (SM/Cer) exhibits the required detergent resistance. In detergent-free membranes composed of different mixtures of SM and Cer (5-30 mol % of Cer) differential scanning calorimetry, fluorescence spectroscopy, and fluorescence microscopy experiments reveal the presence of discrete, Cer-enriched gel domains in a broad temperature range. In particular, at temperatures below SM phase transition ( approximately 40 degrees C) two gel (respectively Cer-rich and SM-rich) phases are directly observed using fluorescence microscopy. Although pure SM membranes are fully solubilized by Triton X-100 at room temperature, 5 mol % Cer is also enough to induce detergent resistance, even with a large detergent excess and lengthy equilibration times. Short-chain Cers do not give rise to detergent resistance. SM/Cer mixtures containing up to 30 mol % Cer become fully soluble at approximately 50 degrees C, i.e., well above the gel-fluid transition temperature of SM. The combined results of temperature-dependent solubilization and differential scanning calorimetry reveal that SM-rich domains are preferentially solubilized over the Cer-rich ones as soon as the former melt (i.e., at approximately 40 degrees C). As a consequence, at temperatures allowing only partial solubilization, the nonsolubilized residue is enriched in Cer with respect to the original bilayer composition. Fluorescence microscopy of giant unilamellar vesicles at room temperature clearly shows that SM-rich domains are preferentially solubilized over the Cer-rich ones and that the latter become more rigid and extensive as a consequence of the detergent effects. These observations may be relevant to the phenomena of sphingomyelinase-dependent signaling, generation of "raft platforms", and detergent-resistant cell membranes.

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Section: Detergent Resistancesupporting

confidence: 86%

Detergent-Resistant, Ceramide-Enriched Domains in Sphingomyelin/Ceramide Bilayers

Sot

Bagatolli

Goñi

et al. 2006

Biophysical Journal

Self Cite

144

128

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“…This observation provides clear support to the idea that the so-called detergent-resistant membranes, actually fractions derived from animal cell plasma membranes, resist solubilization by Triton X-100 because they are in the liquid-ordered state . Highly ordered lipid domains would inhibit the insertion of detergent monomers, commonly accepted as the first step in membrane solubilization. , In fact, in the extreme case of the purple membrane of Halobacterium , in which lipids form two-dimensional crystalline assays, we have proposed that detergent insertion is virtually impossible, with the surfactant binding only the periphery of the purple membrane patches …”

Section: Discussionsupporting

confidence: 60%

Equilibrium and Kinetic Studies of the Solubilization of Phospholipid−Cholesterol Bilayers by C12E8. The Influence of the Lipid Phase Structure

et al. 1999

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The influence of the lipidic phase structures on their susceptibility to solubilization by the nonionic detergent C12E8 has been explored. To this aim, a phase diagram for dimyristoylphosphatidylcholine/cholesterol in excess water has been constructed in which phase boundaries were derived from high-sensitivity differential scanning calorimetry. Six different lamellar phases can be obtained with this system, namely crystalline (Lc‘), gel (Lβ‘ or Lβ), rippled (Pβ‘), liquid crystalline or fluid (Lα), gellike liquid ordered (Loβ), and fluidlike liquid ordered (Loα). The solubilization of samples in each of these phases by C12E8 has been studied through changes in suspension turbidity under equilibrium conditions and also using a stopped-flow time-resolved technique. We find that variations in temperature and cholesterol content within a single phase can affect the equilibrium and kinetic parameters of detergent solubilization somewhat, particularly in the former case. However, much larger variations in the equilibrium and kinetics parameters of C12E8 solubilization are noted between different phases, particularly those phases containing cholesterol. In general, the presence of cholesterol potentiates the solubilization of DMPC vesicles at lower temperatures and inhibits their solubilization at higher temperatures. Moreover, in the more fluid phases (Lα for DMPC alone or Loβ and Loα for DMPC−cholesterol mixtures), vesicle turbidity was not affected by detergent concentration until concentration near the solubilization concentration was reached, at which point an increase in turbidity attributed to vesicle lysis and reassembly occurs prior to vesicle solubilization. In contrast, this effect is markedly reduced in the various gel phases of DMPC alone, where vesicle turbidity generally decreases monotonically with detergent concentration. Cholesterol-induced liquid crystalline-like liquid ordered phases (Loα), that are presumed to coexist with the Lα phase in animal cell membranes, are much more resistant to solubilization than the predominant fluid disordered Lα phase, present in such membranes.

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“…One possibility is that the detergent does not mix well with lipids in the gel phase, so that it accumulates at lattice defects and fragments of gel bilayer surrounded by detergent instead of true micelles (i.e., more or less spherical structures containing molecular mixtures of lipid and detergent) are formed. Such a possibility was suggested for the solubilization of Halobacterium purple membranes that exist in the bilayer crystalline state (39). This would mean that saturation occurs through a different mechanism in the fluid and in the gel phases, as supported by the data in Funari et al (22).…”

Section: Discussionmentioning

confidence: 86%

Lipid Bilayers in the Gel Phase Become Saturated by Triton X-100 at Lower Surfactant Concentrations Than Those in the Fluid Phase

Ahyayauch

Collado

Alonso

et al. 2012

Biophysical Journal

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It has been repeatedly observed that lipid bilayers in the gel phase are solubilized by lower concentrations of Triton X-100, at least within certain temperature ranges, or other nonionic detergents than bilayers in the fluid phase. In a previous study, we showed that detergent partition coefficients into the lipid bilayer were the same for the gel and the fluid phases. In this contribution, turbidity, calorimetry, and 31P-NMR concur in showing that bilayers in the gel state (at least down to 13-20°C below the gel-fluid transition temperature) become saturated with detergent at lower detergent concentrations than those in the fluid state, irrespective of temperature. The different saturation may explain the observed differences in solubilization.

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Early and delayed stages in the solubilization of purple membrane by a polyoxyethylenic surfactant

Cited by 11 publications

References 19 publications

Detergent-Resistant, Ceramide-Enriched Domains in Sphingomyelin/Ceramide Bilayers

Detergent-Resistant, Ceramide-Enriched Domains in Sphingomyelin/Ceramide Bilayers

Equilibrium and Kinetic Studies of the Solubilization of Phospholipid−Cholesterol Bilayers by C12E8. The Influence of the Lipid Phase Structure

Lipid Bilayers in the Gel Phase Become Saturated by Triton X-100 at Lower Surfactant Concentrations Than Those in the Fluid Phase

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