Further study of the chemical structure of the equine erythrocyte hematoside containing O-acetyl ester.

The chemical structure of an equine hematoside, which contained an ester group and comprised 72% of the total erythrocyte gangliosides, was determined by means of nondestructive and destructive procedures. A 400-MHz nuclear magnetic resonance spectrum of the ganglioside in perdeuterodimethyl sulfoxide demonstrated three protons due to a methyl group of an acetyl moiety, as well as amide and anomeric protons which were compatible with those of the ordinary hematoside. The spin decoupling difference spectroscopy of the ganglioside revealed the presence of the following structures. [formula: see text]. A mass spectrum obtained by direct probe analysis of the permethylated ganglioside demonstrated the presence of an O-acetyl-N-glycolylneuraminic acid moiety (m/z 434). Gas chromatography-mass spectrometric analysis of the sialic acid, derivatives from the periodate-oxidized ganglioside, and derivatives from acetalized ganglioside prepared under controlled conditions indicated that the sialic acid of the ganglioside was 4-O-acetyl-N-glycolylneuraminic acid. Thus, the structure of the equine ganglioside was determined as 4-O-acetyl-N-glycolylneuraminyl alpha 2-3 galactosyl beta 1-4 glucosyl beta 1-ceramide. The antigenic properties of this ganglioside were examined. In contrast to ordinary hematoside, which reacted strongly with Hanganutziu-Deicher (H-D) antibodies of a heterophile type in human, this ganglioside did not exhibit any H-D antigenicity. Therefore, a free hydroxy group at C-4 of the N-glycolylneuraminyl moiety in gangliosides appears to be absolutely required for the manifestation of H-D antigenicity.