Abstract
For development of $EMIT-T_{3}$ assay, the conjugation of 3, 5, 3'-triiodothyroformic acid NHS ester to G6PDH was attempted in various reaction conditions. Up to now, the best conjugation condition was the ratio of $T_{3}$-NHS:G6PDH=100 in 25% carbitol-Tris buffer at pH 9, $0^{\circ}C$ during overnight. The obtained $T_{3}$-G6PDH conjugates usually had 20% residual enzyme activity which was inhibited by 40-70% with various $anti-T_{3}$ antibodies. Utilizing the conjugate I and an antibody (S2633G), a useful standard curve for $T_{3}$ assay was obtained in the range of 0 to 5ng/ml with 499 EMIT units of separation.