title: N-iodoacetyltyramine: preparation and use in 125I labeling by alkylation of sulfhydryl groups.
abstract: Preparation and use of N-iodoacetyltyramine in generation of 125I-labeled compounds is described. The kinetics of alkylation of N-acetylcysteine by N-iodoacetyltyramine (k2 = 3.0 M-1 s-1) and N-chloroacetyltyramine (k2 = 0.12 M-1 s-1) indicate that N-iodoacetyltyramine is more useful for labeling sulfhydryl-containing compounds to high specific activity with 125I. Conditions for preparation of carrier-free 125I-labeled N-iodoacetyl-3-monoiodotyramine in 50% yield based on starting iodide are described. The high degree of group specificity of N-iodoacetyl-3-monoiodotyramine reaction with sulfhydryl groups is demonstrated by the high reactivity toward sulfhydryl-containing bovine serum albumin and low reactivity toward N-ethylmaleimide-blocked bovine serum albumin and IgG. 125I-labeled N-iodoacetyl-3-monoiodotyramine was also used to prepare an 125I-labeled ACTH derivative that retains full biological activity, further demonstrating the selectivity toward reactions with sulfhydryl groups.
authors.affiliation: Department of Biochemistry, University of Nebraska, Lincoln 68583-0718.
authors.forename: C M
authors.initials: CM
authors.lastname: Lin
authors.forename: K A
authors.initials: KA
authors.lastname: Mihal
authors.forename: R J
authors.initials: RJ
authors.lastname: Krueger
mesh_terms: D000302:Adrenal Cortex / Q000166:cytology; D000324:Adrenocorticotropic Hormone; D000478:Alkylation; D000818:Animals; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003345:Corticosterone / Q000032:analysis / Q000096:biosynthesis; D007457:Iodine Radioisotopes; D008297:Male; D051381:Rats; D013379:Substrate Specificity; D013438:Sulfhydryl Compounds; D014439:Tyramine / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis / Q000302:isolation & purification
chemical_list: D007457:Iodine Radioisotopes; D013438:Sulfhydryl Compounds; C060830:N-iodoacetyltyramine; D000324:Adrenocorticotropic Hormone; D003345:Corticosterone; D014439:Tyramine