CHEMICAL AND SEROLOGICAL STUDIES WITH AN IODINE-CONTAINING SYNTHETIC IMMUNOLOGICAL DETERMINANT 4-HYDROXY-3-IODO-5-NITROPHENYLACETIC ACID (NIP) AND RELATED COMPOUNDS

Abstract

The synthesis and properties of 4-hydroxy-3-iodo-5-nitrophenylacetic acid (NIP) and several related compounds are described. Conjugates of NIP with proteins are prepared from the azide, synthesized from commercial 4-hydroxyphenylacetic acid. Sera from rabbits and mice immunized with NIP-ovalbumin or NIP-chicken serum globulin bind N131IP -containing compounds, as judged from precipitation of radioactivity by salting-out of immunoglobulins. Homogeneous binding is obtained with N131 IP-polyly-sine, N131 IP-[epsilon]-amino-n-caproic acid (N131 IP[long dash]aminocap), and other structurally related haptens; non-homogeneous binding is obtained with Nl31jp[long dash]bovine serum albumin. Binding to salt-precipitated immuno-globulin of N131 IP[long dash]aminocap, the hapten of choice for this purpose, provides an assay for antibody measurable at concentrations down to at least M-9 serum binding capacity ([image]0.1 [mu]g antibody/ml). Structurally related compounds and NIP[long dash]protein conjugates competitively inhibit binding of N131 IP[long dash]aminocap. The inhibitions indicate that the iodine contained in NIP, but not the carrier protein, contributes significantly to the binding site.