A for alanine or adenine B for ambiguous asparagine/aspartic-acid R for arginine N for asparagine D for aspartic-acid C for cysteine or cystine or cytosine Q for glutamine E for glutamic-acid Z for ambiguous glutamine/glutamic acid G for glycine or guanine H for histidine I for isoleucine L for leucine K for lysine M for methionine F for phenylalanine P for proline S for serine T for threonine or thymine W for tryptophan Y for tyrosine V for valine U for uracil O for water X for other