HIGH IODINATION OF ANTISERUM GLOBULINS WITH I127
ARMY BIOLOGICAL LABS FREDERICK MD
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Brucella antiglobulins were highly iodinated with nonradioactive I127 to determine the extent to which oxidation by iodine is responsible for loss of antibody activity. As many as 51 atoms of iodine were bound to a molecule of antiglobulin without causing loss of activity. Distribution studies of the iodotyrosines formed during iodination showed that both moniodotyrosine dd diiodotyrosine increase with increased iodination levels. When approximately 24 atoms of iodine per molecule of protein have been bound, the former begins to level off while the latter con tinues to rise almost linearly. The two iodo tyrosines are equally distributed in a sample containing about 38 atoms of iodine per molecule of protein. The binding of 51.1 atoms of iodine per molecule of protein corresponds to the iodi nation of about 28 out of a total of 55 tyrosyl residues. It is believed that the remaining 27 tyrosyl residues are buried within the protein molecule aome accessible only after the iodine penetrates the exposed protective groups surrounding the molecule. Ultraviolet spectro photometry methods for rapid estimation of bound iodine atoms and the number of iodotyrosyl residues in a sample of iodinated protein are described.