Thermodynamics of Lipid Membrane Solubilization by Sodium Dodecyl Sulfate

Abstract

We provide a comprehensive thermodynamic description of lipid membrane dissolution by a charged detergent. To this end, we have studied the interactions between the anionic detergent sodium dodecyl sulfate (SDS) and the zwitterionic phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) in dilute aqueous solution (10 mM phosphate buffer, 154 mM NaCl, pH 7.4). Thermodynamic parameters of vesicle solubilization and reconstitution, membrane partitioning, and micelle formation were assessed by right-angle light scattering and isothermal titration calorimetry. Membrane translocation and dissolution proceed very slowly at 25 degrees C but are considerably accelerated at 65 degrees C. At this temperature, a simple SDS/POPC phase diagram (comprising vesicular, coexistence, and micellar ranges) and a complete set of partition coefficients and transfer enthalpies were obtained. Electrostatic repulsion effects at the membrane surface were implemented by combining Gouy-Chapman theory with a Langmuir adsorption isotherm to account for Na+ binding to membrane-incorporated DS-. This approach offered a quantitative understanding of solubilization and reconstitution processes, which were interpreted in terms of partition equilibria between and ideal mixing in all phases. More than any other property, the transbilayer flip-flop rate under given experimental conditions hence appears to dictate a detergent's suitability for thermodynamically controlled lipid membrane solubilization and reconstitution.

Factors altering the membrane fluidity of spinach thylakoid as determined by fluorescence polarization

“…SDS is an ionic surfactant that can effectively interact with protein at low millimolar concentration levels (Kopanchur and Rinken 2001). SDS is a valuable tool in membrane biochemistry (Garavito and Ferguson-Miller 2001) that has been effectively used for solubilization of membrane proteins, photosynthetic pigments and/or phospholipids (Yang et al 1996;Keller et al 2006). In this study, the alteration in fluidity of spinach thylakoid membranes by SDS was shown in Fig.…”

Membranolytic Activity of Bile Salts: Influence of Biological Membrane Properties and Composition

“…for SDS, between 50 and 80 SDS monomers per micelle [23,[25][26][27]. The size and shape of micelles and aggregation number is dependent on the environmental conditions like ionic strength, pH, temperature etc.…”

A thermodynamic analysis of the binding interaction between polysorbate 20 and 80 with human serum albumins and immunoglobulins: A contribution to understand colloidal protein stabilisation

“…Especially for the prevention of physical degradation, surface active agents like detergents are often necessary [17,18]. Therefore, a number of biophysical techniques are used to investigate and understand protein-excipient interactions [6,[23][24][25][26][27][28][29][30]. Detergents are amphiphilic in nature, containing a hydrophilic head group and a hydrophobic part, and this dual property causes detergents to adopt a specific orientation at interfaces and in aqueous solutions.…”