any derivative of an amino acid resulting from reaction at an amino group, carboxy group, side-chain functional group, or from the replacement of any hydrogen by a heteroatom. The definition normally excludes peptides containing amino acid residues
"any derivative of an amino acid resulting from reaction at an amino group, carboxy group, side-chain functional group, or from the replacement of any hydrogen by a heteroatom. The definition normally excludes peptides containing amino acid residues"@en