[Condensation of residues of diiodotyrosine with thyroxine near the surface of the thyroglobulin molecule by means of differential spectrophotometry].

Aromatic amino acids including iodotyrosines and thyroxin in intact, extraiodinated and acetylated bovine thyroglobulin were studied by the differential spectrophotometric technique. Modifications (i. e. acetylation, iodination) changed the accessibility of these chromophores to ethylene glycol. The data obtained suggest that thyroxin can be formed from two diiodotyrosine residues in the surface regions of the thyroglobulin molecule which are available for ethylene glycol.