RADIOLABELED BIOTIN AMIDES FROM TRIAZENYL PRECURSORS - SYNTHESIS, BINDING, AND IN-VIVO PROPERTIES

The synthesis of N-(4-[I-127/125/123]iodobenzyl)biotin amides 4a - 4c performed by the direct decomposition of N-[4-(3',3'-dimethyltriazenyl )benzyl]biotin amide with sodium iodide in the presence of CF3COOH is described. Iodinated in this way biotin formed a stable complex with a vidin (K-d = 2.84 +/- 0.45 x 10(-15) M, n = 3.9 +/- 0.6) which dissoci ated in the presence of excess native biotin with a rate constant of 0 .034 +/- 0.006 hr(-1). Blood clearance studies and the lack of thyroid uptake indicated that this compound was not deiodinated in vivo and b ehaved in circulation much like native biotin. This aryltriazene precu rsor method is suitable for labeling with short-lived radiohalides. It can be used to produce no-carrier-added derivatives of biotin for use in biologic studies and assays involving avidin or streptavidin.