What is the status of peptide nucleic acid (PNA) residues in amino acid 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.

According to MPEP 2412.03(b), peptide nucleic acid (PNA) residues have a special status in amino acid sequence listings. The MPEP clearly states:

“A peptide nucleic acid (PNA) residue is not considered an amino acid, but is considered a nucleotide.”

This distinction is important for patent applicants and examiners because:

• PNA residues should not be included in amino acid sequence listings.
• PNA residues should instead be treated as nucleotides and included in nucleotide sequence listings.
• This classification affects how PNA-containing molecules are represented and searched in patent databases.