Which membrane properties determine detergent resistance?

V.M. TRUCCO; P.M. RODI,; A. M. GENNARO

Montevideo, Uruguay

Congreso; XXXVI Reunión Anual de la Sociedad Argentina de Biofísica, 6th International Conference on Biological Physics y 5th Southern Cone Biophysics Congress; 2007

SAB-IUPAB-IUPAP

The understanding of detergent-lipid interactions may shed light on fundamental membrane problems such as domain formation. It is interesting to clarify which membrane properties are relevant in determining its detergent resistance. In this work, we study the behavior of human and bovine erythrocyte membranes under the action of different concentrations of the non ionic detergent Triton X-100. We quantify the insoluble fraction of membrane phospholipids and determine their lipid composition for different detergent concentrations. We also investigate the solubility behavior of erythrocytes of both species previously depleted in cholesterol with methyl-â-cyclodextrin. In the four systems (intact bovine, cholesterol depleted bovine, intact human and cholesterol depleted human erythrocytes), we find that Triton X-100 solubilizes preferentially phospholipids than cholesterol. By fitting the data of the amount of insoluble lipids as a function of detergent/lipid ratio, we defined a “detergent resistance parameter”. We found that this parameter is correlated with the total amount of cholesterol plus sphingomyelin in each membrane. Resistance to detergent solubilization is also correlated to the degree of lipid ordering in the original membranes quantified by spin label EPR. The hypothesis of the presence of lipid domains in the erythrocyte membrane is discussed on the basis of the present results.