Editor's note: Citation Classics Commentaries were written by the authors of some of studies that were the most highly cited papers between 1961 and 1975. The essays were originally published between 1977 and 1993 in Current Contents, a publication of the Institute for Scientific Information (ISI), now Thomson Scientific. (ISI was founded by Eugene Garfield, also the founder of The Scientist.) This essay has been edited for space.
As a young chemist at Columbia University in 1956, one of Ronald Breslow's first research goals was to solve the mystery of how the enzyme thiamine pyrophosphate catalyzed biochemical reactions such as the Krebs cycle and photosynthesis. He used nuclear magnetic resonance to capture the subatomic properties of the reaction. Breslow can't recall exactly what he exclaimed when he first saw a hydrogen atom from the compound exchange with deuterium oxide. "Maybe I shouted 'Hot Dog!' I don't ...
