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The decapeptide Arg-Gly-Asp-Ser-Cys-Arg-Gly-Asp-Ser-Tyr, which contains two Arg-Gly-Asp (RGD) moieties in its sequence, has been successfully labeled with radioactive rhenium (Re-188) yielding a single, stable oxorhenium complex. This complex is being evaluated for possible application in oncology as a target-specific radiotherapeutic agent, because its radioactive technetium-99m analogue has already been applied for the scintigraphic detection of malignant melanoma in humans. For structural characterization purposes, the complex of the decapeptide was synthesized at the macroscopic level using nonradioactive rhenium (Re-185/Re-187). NMR and mass spectral analysis of the nonradioactive oxorhenium complex revealed that the decapeptide coordinates to the oxorhenium core through the N(amide) of Asp3, the N(amide) of Ser4, and the N(amide) and S(thiolate) atoms of Cys5 to form a complex of the ReO[N(3)S] type.

Quality Control (QC) of radiopharmaceuticals is important, providing products of high standards. The current study refers to an enzymic radioiodination method applied to the labeling of antibodies used in nuclear medicine and to the respective QC procedures. Readily available materials such as 125I, polyclonal immunoglobulin G (IgG) and a collection of simple chromatographic techniques helped establish a QC protocol suitable for the radiochemical evaluation of radioiodinated biomolecules. A high pre-purification radiolabeling yield (90%) for total protein was detected by paper electrophoresis (PE) and size exclusion chromatography (SEC), but only the inclusion of SDS-PAGE confirmed the existence of "self-iodination" of lactoperoxidase (LPO) and revealed the true radiolabeling yield for 125I-IgG (79%).

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