Laser-light scattering investigation of the micellar properties of gangliosides.

The micellar properties of gangliosides in water solutions were investigated by quasielastic light scattering measurements. GM1 and GD1a gangliosides were isolated from calf brain, purified to more than 99% and dissolved in 0.025 M Tris--HCl buffer (pH 6.8) at 37 degrees C. The average intensity of scattered light and the intensity correlation function were measured by an apparatus including a 5145 A argon laser and a real-time digital correlator. The scattered intensity data allowed the derivation of an upper limit to the critical micelle concentration (c0) and the evaluation of the molecular weight (M) of the micelle. The intensity correlation function gave the diffusion coefficient D, and hence the hydrodynamic radius RH, and also contained information on the polydispersity of the sample. We find co less than 1 x 10(-6) M for both GM1 and GD1a, M = 532000 +/- 50000 and RH = 63.9 +/- 2 A for GM1, and M = 417000 +/- 40000 and RH = 59.5 +/- 2 A for GD1a. The mixture 3:1 of the two gangliosides gave intermediate values for all examined parameters. The presence of cations, within the physiological concentration range, and, in particular of Ca2+, did not influence significantly the values of co and the main features of the micelle.