OPTIMAL CONDITIONS TO RADIOLABEL (H-3 OR C-14) AMINOSUGAR-CONTAINING GLYCOSPHINGOLIPIDS BY DE-N-ACETYLATION AND RE-N-ACETYLATION

The optimal conditions were examined for selective re-N-acetylation wi th C-14 or H-3 acetic anhydride of de-N-acetylated aminosugar-containi ng glycosphingolipids. Re-N-acetylation, which is nearly quantitative within 10 minutes in methanol, occurs selectively up to a maximal 100% yield when using a molar ratio of 5 mol of acetic anhydride per mole of aminosugar present in the glycosphingolipid. Above this molar ratio , it was observed some O-acetylation of carbohydrates which could be r emoved by mild alkali treatment. The method allows the choice of C-14- or H-3-labeling of glycosphingolipids with a final specific radioacti vity which depends solely on the one of acetic anhydride. The binding of specific antibodies to glycosphingolipids, which was abolished upon de-N-acetylation, was again detectable after re-N-acetylation with ra dioactive acetic anhydride, suggesting that the native structures were recovered. This procedure of radiolabeling offers safety, rapidity an d broad applicability to alkali-stable aminosugar-containing glycosphi ngolipids.