Studies on the chemical basis of the antigenicity of proteins. 2. Antigenic specificity of polytyrosyl gelatins

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Abstract
Three polytyrosyl gelatins differing in their tyrosine content, as well as a gelatin enriched with both tyrosine and glutamic acid, were synthesized and tested for their antigenicity in rabbits. All antisera gave positive precipitin tests. The extent of the antigenicity of the gelatin derivatives investigated depends on the amount of tyrosine attached. As little as 2% of tyrosine suffices to enhance strongly the antigenicity of gelatin. The serological specificity of the gelatin derivatives changes strongly as a function of their tyrosine content. The specificity of compounds rich in tyrosine resides almost exclusively in the peptide chains attached, whereas it resides essentially only in the gelatin moiety in the derivative containing only 2% of tyrosine residues. The attachment to gelatin of the polar glutamic acid in addition to tyrosine yielded an antigen of very narrow specificity. Electrophoretic experiments have shown that the antigen which is not precipitated in the equivalence zone is bound to non-precipitable antibodies in the form of a soluble complex.