Protein radiohalogenation: observations on the design of N-succinimidyl ester acylation agents.
In previous studies we have demonstrated that antibodies radioiodinated with N-succinimidyl 3-iodobenzoate (SIB) are less susceptible to loss of radioiodine in vivo than antibodies iodinated directly by electrophilic substitution on their tyrosine residues with Iodogen. Since the Bolton-Hunter reagent, N-succinimidyl 3-(4-hydroxy-3-iodophenyl)propionate, is identical with SIB except that it contains a hydroxyl group on the aromatic ring and a two-methylene spacer, a comparison of their coupling chemistry and in vivo behavior was performed to better understand the structural requirements for a useful iodinated acylation agent. Protein concentration and pH had a significant effect on the coupling efficiency of both SIB and the Bolton-Hunter reagent; however, protein-labeling yields with SIB were generally higher by a factor of 2. Paired-label biodistribution studies in mice demonstrated that thyroid uptake (a monitor of dehalogenation) of antibody labeled by the Bolton-Hunter method was twice that of antibody labeled with SIB but only 7% of that observed for antibody labeled with Iodogen. These results suggest that even minor differences in iodination site can profoundly alter the retention of label on a protein in vivo.
Vaidyanathan
G
G
Duke University Medical Center, Department of Radiology, Durham, North Carolina 27710.
Zalutsky
M R
MR
D000107:Acetylation; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D006041:Goats; D007457:Iodine Radioisotopes / Q000737:chemistry* / Q000493:pharmacokinetics; D007463:Iodobenzoates / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D011506:Proteins / Q000737:chemistry* / Q000493:pharmacokinetics; D013388:Succinimides / Q000138:chemical synthesis* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D013961:Thyroid Gland / Q000378:metabolism; D014018:Tissue Distribution
D000911:Antibodies, Monoclonal; D007457:Iodine Radioisotopes; D007463:Iodobenzoates; D011506:Proteins; D013388:Succinimides; C022581:Bolton-Hunter reagent; C062337:N-succinimidyl 3-iodobenzoate