DEPENDENCE OF THE FORM-FACTOR OF GANGLIOSIDE MICELLES ON A CONFORMATIONAL CHANGE WITH TEMPERATURE

The gangliosides GM2, GM1 and GD1b, biological amphiphiles with a doub le tail hydrophobic part and an oligosaccharide chain headgroup, form micelles in solution. Light scattering experiments have shown that gan glioside micelles which have gone through a temperature cycle have a s maller molecular mass and hydrodynamic radius than those which have be en kept at room temperature. This fact has been interpreted with the h ypothesis that, with temperature, the ganglioside molecules undergo a conformational change which affects their micellar properties apprecia bly. Careful small angle X-ray experiments, aimed to confirm the light scattering data and to evidence differences in the micellar internal structure are presented. Ganglioside micelles are quite inhomogeneous particles with respect to X-ray scattering, since there is a large con trast variation between the inner lipid part and the external hydrated sugar layer. Experimental form factors are fitted with a double-shell oblate-ellipsoid model.