amino-acid residue modified amino-acid residue An amino acid residue that results from covalent modification or chemical alteration to the side chain or backbone atoms of the residue or derivative thereof, where such alteration maintains the integrity of the amino acid chain containing the residue. Category=external. Note: This entity is distinct from MOD:00000 "protein modification" in that the latter includes canonical amino acid residues that replaced other canonical amino acid residues in the context of an amino acid chain. [PRO:DAN] PR:000025513 modified amino acid chain residue modified protein residue protein unmodified amino-acid residue