Tryptophan
Tryptophan is an essential amino acid that must be obtained from the human diet. It has the single amino acid code W (see single letter amino acid codes) and the 3 letter code Trp. It is coded for in the genome by the nucleotide base sequence UGG [1].
Medical Uses
Tryptophan is also a drug which is used to treat depression, when other antidepressants have been otherwise uneffective.