As mentioned above, in different structures, the same ligand could interact with a metal ion using different atoms. For example, 5-acetamido-1,3,4-thiadiazole-2-sulfonamide (AZM, Figure ) was found to interact with Zn 2+ in 32 PDB structures. In most cases, either nitrogen or oxygen was the chelating atom, but in some complexes both atoms were coordinated to the ion. Since the metal chelating groups were defined based on the atoms interacting with the metal ion (Scheme 1), for ligands that interacted with metal ions in different ways, more than one metal-chelating group could be extracted. At least one metal-chelating group could be extracted from over 90% of the ligands found for each metal ion (Table , full list in S3 of the Supporting Information). For the remaining ligands, the extraction pipeline failed due to errors in the ligand stru ctures. The extraction resulted in 626 unique metal-chelating groups for Mg 2+ , 397 for Mn 2+ , and 560 for Zn 2+ , amounting to a total of 1,223 unique chelating groups. Once again, an overlap was observed among the metal-chelating groups extracted from ligands for the different investigated ions. In total, 83 metal-chelating groups interacted with all investigated ions, while 98 interacted with both Mg 2+ and Mn 2+ , 50 with both Mn 2+ and Zn 2+ , and 46 with both Mg 2+ and Zn 2+ (Figure ). [a] 1,223 unique metal-chelating groups across all metal ions. 521 unique metal-chelating groups containing a phosphorus atom across all metal ions.