SUMMARYThe fixation of tetanus toxin by brain ganglioside has been confirmed. A method has been developed for assaying the toxin-fixing capacity of ganglioside in the analytical ultracentrifuge. Under appropriate conditions ganglioside will fix many times its own weight of toxin. Ganglioside preparations from brain contain a t least three gangliosides; at least two of these differ in their sialic acid contents and toxinfixing capacities. The sialic acid residues (and their free carboxyl groups) are essential for toxin-fixation. Tetanus toxin does not appear (so far) to bring about any change in the ganglioside molecule.
SUMMARYAlthough tetanus toxin is fixed by brain ganglioside, it is not fixed by a number of substances more or less closely related to brain ganglioside, or by naturally occurring brain ganglioside not containing hexosamine, or by a hexosamine-containing ganglioside from Tay-Sachs brain. Isolated brain gangliosides may vary considerably in their toxin-fixing capacities.In chloroform + methanol extracts of brain a number of gangliosides which differ in ability to fix toxin can be separated chromatographically. Complexes of ganglioside with phrenosine and sphingomyelin have diminished toxin-fixing capacity. Tetanus toxin and ganglioside have a high binding capacity for calcium, but calcium does not affect the fixation of toxin by ganglioside. Ganglioside fixes strychnine, brucine and thebaine , drugs which have the same neurophysiological activity as tetanus toxin. Ganglioside does not fix y-aminobutyric acid, P-hydroxy-y-aminobutyric acid, histamine, adrenaline, noradrenaline or dopamine, but it does fix serotonin and a number of related compounds. It has been confirmed that albumin is fixed to a small extent by ganglioside at low salt concentration, but (unlike tetanus toxin) this fixation is practically abolished at physiological salt concentration.
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