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NCBI PubChem has gone live with it's new "biologic description" section, which includes HELM strings. Please see below for some examples:
A peptide Example - a peptide HELM for oxytocin
https://pubchem.ncbi.nlm.nih.gov/compound/439302#section=Biologic-Description
A nucleic acid HELM for 5'-thymidylic acid
https://pubchem.ncbi.nlm.nih.gov/compound/9700#section=Biologic-Line-Notation
Support for carbohydrates (including iconographic depictions):
https://pubchem.ncbi.nlm.nih.gov/compound/196569#section=Biologic-Description
EBI ChEMBL
The EBI has generated HELM notation for just under 19K peptides that were previously associated with Mol files in the database and that contain at least three amino acids. This notation is available in the BIOTHERAPEUTICS table and also shown on the Compound Report Card. for example https://www.ebi.ac.uk/chembl/compound/inspect/CHEMBL1252
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