Vincent du Vigneaud (1901-1978) was awarded the 1955 Nobel Prize in Chemistry for his work on biochemically important sulphur compounds and for the first synthesis of a polypeptide hormone. du Vigneaud's scientific research encompassed a wide focus, from insulin to cysteine, methionine, biotin (vitamin B7), oxytocin (a mammalian brain hormone and neurotransmitter), and vasopressin (a brain peptide hormone). In the late 1930s and early 1940s, he identified the chemical structure of insulin and established the structure of the sulfur-bearing biotin. Later, he isolated vasopressin and oxytocin and analyzed their chemical structure. In 1953, he synthesized oxytocin and became the first to achieve the synthesis of a protein hormone. du Vigneaud also studied intermediary metabolism (a process in which energy is extracted from cellular nutrients and used to build cellular components), transmethylation (the transfer of a methyl group between two compounds) and metabolism of one-carbon compounds, and transsulfuration (a process by which homocysteine is metabolized into cysteine).