Gangliosides are acidic glycosphingolipids that form lipid rafts in the outer leaflet of the cell plasma membrane, especially in neuronal cells in the central nervous system. They participate in cellular proliferation, differentiation, adhesion, signal transduction, cell-to-cell interactions, tumorigenesis and metastasis. The accumulation of gangliosides has been linked to several diseases. Ganglioside GD1b may act as a bacterial toxin receptor (tetanus, botulinus). High levels are found in gliomas and astrocytomas. It modulates protein kinase activities. In vivo and in vitro it is in equilibrium with the lactone structure.