Similarity of copper and technetium binding sites in human IgG

Kits for direct labeling of IgG with 99mTc were used without modification for the preparation of [67Cu]IgG. The IgG was pre-treated to generate thiolate groups which would bind 67Cu. The direct labeling of reduced IgG with 67Cu was highly efficient, resulting in approx. 95% 67Cu binding. Non-reduced IgG (negative control) had labeling efficiencies of less than 10%. IgG pre-exposed to Cu(II) had reduced amounts of 99mTc bound to it. The results demonstrate a direct relationship between copper- and 99mTc-binding sites in IgG.