During his Lakeside Hospital internship, Zamecnik became interested in how cells regulate growth, and hence, in protein chemistry. He was awarded a Finney-Howell Fellowship and a Moseley Traveling Fellowship to go to the Carlsberg Laboratory in Copenhagen where he worked with Dr. Kai Linderstrom-Lang. His planned time in Copenhagen was cut short because of World War II—the Germans occupied Denmark from April 1940—and he and his wife, Mary Connor, returned to Boston where he became an Assistant Physician at the Huntington Memorial Hospital, studying the toxic factors involved in traumatic shock for a wartime Office of Scientific Research and Development project led by Huntington director Joseph Charles Aub. After a year in New York at the Rockefeller Institute for Medical Research studying protein synthesis with Max Bergmann, he returned to Harvard in 1942 to join the Faculty of Medicine at Harvard Medical School where he became Instructor and then Professor of Medicine, where he served until retiring as the Collis P. Huntington Professor of Oncologic Medicine, Emeritus in 1979.Rheinberger, pp. 38-39
