Self-assembly properties and biomembrane partition equilibrium of two different detergents

M.D. BOCCO GIANELLO; P.M. RODI; A.M. GENNARO

Buzios, Río de Janeiro

Congreso; 2° Congress of the Latinoamerican Federation of Biophysical Societies (LaFEBS) y “XXXVII Congress of the Brazilian Biophysical Society”,; 2012

Latinoamerican Federation of Biophysical Societies

Detergents are essential reactancts for the study of biological membranes. They are frequently used to solubilize membrane proteins and to investigate the interactions among membrane lipid components. In order to obtain a correct description of these phenomena, it is neccesary to obtain information about the interactions among detergent molecules in aqueous solutions leading to self-aggregation and the formation of micellar structures in different conditions. In this work we carry out a comparative study of the self assembly and membrane partition properties of two detergents: Triton X-100 (non ionic) and CHAPS (zwitterionic). We prepared solutions of these detergents in which the liposoluble spin labels n-SASL (n=5, 12 or 16) were added. From the EPR spectra we obtained parameters related to lipid order and water penetration, leading to a characterization of the micellar structures formed at different detergent concentrations. A singular behavior was observed for CHAPS, as significant changes in the aggregates appear when detergent concentration is increased. Applying Factor Analysis, we could determine that the complete behavior of the EPR spectra can be described considering that a second type of micelle appears at high detergent concentrations. Instead, Triton X-100 micelles do not show changes in their EPR spectra as a function of concentration. On the other side, we determine the range of sub-lytic concentrations in order to study the partition equilibrium between the aqueous phase and the erythrocyte membrane. EPR experiments showed that both detergents disorder the lipid bilayer, and CHAPS insertion lead to stomatocytic shapes.