# Unable to generate topology for ligand IOD. PRODRG did not create the required output **URL:** \ **Category:** HADDOCK\ **Created:** [August 18, 2020, 8:14am UTC](https://ask.bioexcel.eu/t/unable-to-generate-topology-for-ligand-iod-prodrg-did-not-create-the-required-output/2404 "2020-08-18T08:14:20Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![mieczyslaw](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@mieczyslaw](https://ask.bioexcel.eu/u/mieczyslaw)\ **Post date:** [August 18, 2020, 8:14am UTC](https://ask.bioexcel.eu/t/unable-to-generate-topology-for-ligand-iod-prodrg-did-not-create-the-required-output/2404/1 "2020-08-18T08:14:20Z")
I submitted PDB structures via HADDOCK Server 2.4, which contain iodine, e.g.: HETATM 2656 I IOD A 311 21.537 36.399 1.691 0.50 28.73 I1- However, the server shows the following error: The following error occurred when processing one of your PDB file: Unable to generate topology for ligand IOD. PRODRG did not create the required output Standalone version also complains on missing IOD in topology. Thanks for your help! ---
**Author:** ![amjjbonvin](https://dub1.discourse-cdn.com/flex013/user_avatar/ask.bioexcel.eu/amjjbonvin/32/23_2.png) [@amjjbonvin](https://ask.bioexcel.eu/u/amjjbonvin)\ **Post date:** [August 18, 2020, 8:29am UTC](https://ask.bioexcel.eu/t/unable-to-generate-topology-for-ligand-iod-prodrg-did-not-create-the-required-output/2404/2 "2020-08-18T08:29:53Z")
You have to follow the proper nomenclature for your ion, which for HADDOCK is: ``` - residue name I1 - atom name I-1 ``` See: [https://bianca.science.uu.nl/haddock2.4/library](https://bianca.science.uu.nl/haddock2.4/library) ---
**Author:** ![mieczyslaw](https://avatars.discourse-cdn.com/v4/letter/m/aeb1de/32.png) [@mieczyslaw](https://ask.bioexcel.eu/u/mieczyslaw)\ **Post date:** [August 18, 2020, 9:15am UTC](https://ask.bioexcel.eu/t/unable-to-generate-topology-for-ligand-iod-prodrg-did-not-create-the-required-output/2404/3 "2020-08-18T09:15:40Z")
Thank you!