Asparagine (ASN)

Asparagine is one of the 20 most common natural amino acids on Earth. It has carboxamide as the side chain's functional group. It is not an essential amino acid. Its codons are AAU and AAC. A reaction between asparagine and reducing sugars or reactive carbonyls produces acrylamide (acrylic amide) in food when heated to sufficient temperature.

Since the asparagine side chain can form hydrogen bond interactions with the peptide backbone, asparagine residues are often found near the beginning and the end of alpha-helices, and in turn motifs in beta sheets. Its role can be thought as "capping" the hydrogen bond interactions that would otherwise be satisfied by the polypeptide backbone. Glutamines, with an extra methylene group, have more conformational entropy and thus are less useful in this regard.