What are the rules for representing modified amino acids in WIPO ST.25 sequence listings?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

The representation of modified amino acids in WIPO ST.25 sequence listings follows specific rules as outlined in MPEP 2423:

“Modified amino acids must be represented as the corresponding unmodified amino acids in the sequence itself if possible. Any modified amino acids appearing in a sequence that cannot otherwise be represented by any other symbol described in Appendix 2, Table 3, must be listed in a feature table.”

Key points for representing modified amino acids:

• Use the standard single-letter code for the corresponding unmodified amino acid in the main sequence
• If the modified amino acid cannot be represented by a standard code, use “X” in the sequence
• List all modified amino acids in the feature table, providing details on the modification
• Use the three-letter abbreviation or full name of the modified amino acid in the feature table

This approach ensures that sequence listings are both standardized and informative, allowing for accurate representation of modified amino acids in patent applications.