This book presents current research in the study of the properties, sources and health benefits of the amino acids tyrosine and aspartic acid. Topics discussed include tyrosine kinases and rheumatoid arthritis; aspartic acid racemisation in the study of ancient DNA in bones; the molecular dynamics simulation for stereoinversion of aspartic acid residues; the physiological role of RTK transactivation in the central nervous system and neuropsychiatric diseases and tyrosines in biological electron transfer.