Immunoassay reagents for thyroid testing. 1. Synthesis of thyroxine conjugates.

Immunoreagents were designed to improve the performance of a commercial fluorescent polarization immunoassay for thyroxine. The thyroxine immunogen was prepared by selective coupling of N-acetyl-L-thyroxine to BSA via an aminocaproic acid spacer arm. The fluorescent tracer was prepared by a multistep reaction sequence which relied on extensive use of orthogonal protecting groups.