tryptophan article 38 controlled study 30 nonhuman 26 priority journal 26 molecular dynamics 22 Humans 20 Tryptophan 20 metabolism 18 Animals 16 enzyme activity 16 human 16 Male 14 Molecular dynamics 14 animal experiment 14 female 14 heme 14 unclassified drug 14 Article 12 Crystallography, X-Ray 12 Female 12 Ligands 12 Oxygen 12 alanine 12 serotonin 12 5 hydroxyindoleacetic acid 10 Amino acids 10 Heme 10 Mutagenesis, Site-Directed 10 Protein Binding 10