A rapid and efficient physiologic chemical method of labeling plasma proteins with indium-111

A rapid physiologic chemical method had been developed for labeling plasma proteins with 111In. Human serum albumin, IgG, fibrinogen, transferrin, lactoferrin and the enzyme bovine thrombin had been successfully labeled with exceptionally high labeling yields of greater than 98%. In vitro bioassays confirmed that 111In-fibrinogen and 111In-thrombin retained 96-99% of their biochemical activities after labeling with the radionuclide. All radiolabeled proteins were stable at 2-8 degrees C in excess of 3 week periods without elution of the "label" or any significant loss of biological activity.