Standard Residues

Standard residues (standard amino acids and nucleotides) are defined in the Protein Data Bank file format (PDB format) (which was updated on August 1, 2007), and have record type ATOM in PDB-format atomic coordinate files. Standard residues are:

   * The 20 standard amino acids, plus ambiguous residue codes ASX, GLX, and undetermined UNK.
   * Six standard nucleotides A, C, G, I, T, U plus UNK. (The PDB file format residue codes make no distinction between ribo- and deoxyribonucleotides.)
   * Modified standard nucleotides designated +A, +C, +G, +I, +T, +U.