The Role of Free Amino Groups in the Blood Group Activity of M and N Mucoids

The M and N blood group substances were treated with different amino‐group reagents, such as: acetic‐, succinic‐, and phthalic‐anhydrides, benzyloxycarbonylchloride, dinitrofluorobenzene, nitrous acid and O‐methyl‐isourea. It was shown that htese reagents blocked or destroyed 2–4 free amino groups (mainly lysine ɛ‐NH2 groups) per one subunit of M or N blood group substance of mol. wt. 30,000. No other effects were found under the conditions used. The blocking or decomposition of amino groups, connected with the loss of their positive charge, lowered the blood activity of M and N mucoids and did not decrease their activity towards phytoagglutinins and the inhibitory activity of viral hemagglutination. The guanidylation of amino groups did not destroy the blood group activity of M and N mucoids.