How should modified and unusual amino acids be represented in a sequence listing?

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 MPEP 2423.01 provides specific guidance on representing modified and unusual amino acids in a sequence listing:

“Modified and unusual amino acids must be represented as the corresponding unmodified amino acids in the sequence itself but may be further described in the feature section of the sequence listing.”

This means that:

• In the main sequence, use the symbol for the corresponding unmodified amino acid.
• Provide additional details about the modification in the feature section of the sequence listing.

This approach ensures that the primary sequence can be easily read and analyzed, while still capturing important information about modifications.