Paul Delos Boyer (1918 - present) received one quarter of the 1997 Nobel Prize in Chemistry for explaining the enzymatic process involved in the production of adenosine triphosphate (ATP). In the early 1950s Boyer began to study how cells form ATP. His work focused on the enzyme ATP synthase, and he demonstrated how the enzyme harnesses the energy produced by hydrogen flow across the mitochondrial membrane to form ATP from adenosine diphosphate (ADP) and inorganic phosphate. This led him to postulate a binding change mechanism for ATP synthesis in which the three catalytic sites on ATP synthase bind ADP and phosphate in sequence and then undergo a conformational change to make a tightly-bound ATP. The sites then change conformation again to release the ATP.