Protein radiohalogenation: observations on the design of N-succinimidyl ester acylation agents

Bioconjug Chem. 1990 Jul-Aug;1(4):269-73. doi: 10.1021/bc00004a007.


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.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acetylation
  • Animals
  • Antibodies, Monoclonal / chemistry
  • Antibodies, Monoclonal / metabolism
  • Antibodies, Monoclonal / pharmacokinetics
  • Goats
  • Iodine Radioisotopes / chemistry*
  • Iodine Radioisotopes / pharmacokinetics
  • Iodobenzoates / chemistry
  • Iodobenzoates / metabolism
  • Iodobenzoates / pharmacology
  • Mice
  • Proteins / chemistry*
  • Proteins / pharmacokinetics
  • Succinimides / chemical synthesis*
  • Succinimides / chemistry
  • Succinimides / metabolism
  • Succinimides / pharmacokinetics
  • Thyroid Gland / metabolism
  • Tissue Distribution


  • Antibodies, Monoclonal
  • Iodine Radioisotopes
  • Iodobenzoates
  • Proteins
  • Succinimides
  • Bolton-Hunter reagent
  • N-succinimidyl 3-iodobenzoate