that organic compounds, which were phosphorylated during metabolic processes, involved oxygen consumption; oxygen consumption was linked to organic compound phosphorylation. His key experiment demonstrated that in frog muscles where glycolysis had been inhibited with iodoacetate, muscular contraction continued for a short period using phosphocreatine as a source of energy. Kalckar referred to this process as “aerobic phosphorylation” (now called oxidative phosphorylation, a biochemical process fundamental to all living organisms). The work was the first demonstration that carbohydrate oxidation and carbohydrate phosphorylation were linked, i.e. the two pathways were directly “coupled.” Furthermore, the study helped establish the basic phenomenon of oxidative phosphorylation, opened the way for its systematic exploration, and suggested for the first time that phosphate compounds acted as a link between catabolism and anabolism. First American Work Upon completing his graduate studies, Kalckar received a Rockefeller research fellowship to spend a year at the California Institute of Technology (Caltech). After arriving in the United States in early 1939, Kalckar briefly visited the Cori lab in St. Louis en route to the west coast. The Coris had unsuccessfully attempted to reproduce Kalckar's oxidative phosphorylation work, and Kalckar was able to point out a key element missing in their experiment. During his St. Louis visit Kalckar and Sidney Colowick (1916–1985) became good friends. Kalckar and his wife arrived in Pasadena in the Spring of 1939 and rapidly became a part of the Caltech social and intellectual community, including Max Delbrück, Linus Pauling, and James and David Bonner. At Delbrück's suggestion he attended C. B. van Niel’s popular Pacific Grove microbiology course, an event that had a lifetime influence on his research career. While at Caltech, Kalckar wrote and published what was, arguably, one of his most important papers. Under Pauling's influence he reviewed the literature dealing with biological energetic mechanisms. In 108 pages, including 310 references, the paper was a virtual synopsis of the state of biochemistry at the time. As Kalckar noted: The aim of this review has been not only to collect and coordinate knowledge from very different fields, like animal physiology, microbiology, enzyme chemistry, organic and physical chemistry, but also to interpret all the fundamental biological phenomena from a dynamic point of view. (p. 167) Although not highly cited, the paper was important because Kalckar provided strong evidence for the role of "high energy" compounds in metabolic processes. In the paper Kalckar developed an argument for the central