Labeling of hematoporphyrin with 105Rh and binding studies with human gamma globulin

Labeling of hematoporphyrin with 105Rh at stoichiometric concentrations is described. Labeling efficiencies of up to 93% could be obtained at pH 9.0 in bicarbonate buffer. Solvent extraction of 105Rh-hematoporphyrin into methyl isobutyl ketone was used to estimate the complex yield. The complex showed high stability and no loss of 105Rh was seen throughout the 6 days of study. 105Rh-hematoporphyrin when incubated with human gamma globulin was seen to be quantitatively bound to the protein. This procedure may be used for labeling monoclonal antibodies with 105Rh for therapeutic applications.