Structural characterization of Cd2 + complexes in solution with DMSA and DMPS

• DMSA and DMPS can both act as chelators for Cd2 +.
• DMPS can bind through two thiolate groups.
• DMSA can bind through one thiolate and one carboxylate groups.
• Both DMPS and DMPS form poly-metallic complexes.

Meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercaptopropane-1-sulfonic acid (DMPS) are chelating agents which have been used clinically to treat patients suffering from Pb2 + or Hg2 + exposure. Cd2 + is a related environmental pollutant that is of increasing public health concern due to a demonstrated dose–response between urinary Cd level and an increased risk of diabetes. However, therapeutically effective chelating agents which enhance the excretion of Cd2 + from humans have yet to be identified. Here we present a structural characterization of complexes of DMSA and DMPS with Cd2 + at physiological pH using a combination of X-ray absorption spectroscopy, size exclusion chromatography and density functional theory. The results indicate a complex chemistry in which multi-metallic forms are important, but are consistent with both DMPS and DMSA acting as true chelators, using two thiolates for DMPS and one thiolate and one carboxylate for DMSA.

X-ray absorption spectroscopy, density functional theory and size exclusion chromatography with element specific detection provide details of the solution structure of Cd2 + complexes in with the chelators dimercaptopropanesulfonic acid and dimercaptosuccinic acid.Figure optionsDownload as PowerPoint slide