Rudolph Arthur Marcus

Rudolph Arthur Marcus, born in 1923, Canadian-American chemist and Nobel Prize winner. Marcus contributed greatly to the understanding of electron-transfer reactions (the movement of electrons from one molecule to another) in chemical systems. He developed a formula, called the Marcus theory, that enabled scientists to predict the pattern and speed of such reactions. This knowledge is vital to the study of biochemical processes and cellular metabolism, and to the production of biosensors and batteries. For this work, Marcus was awarded the 1992 Nobel Prize in chemistry.

Born in Montreal, Québec, Canada, Marcus received his Ph.D. degree in physical chemistry from McGill University in 1946. In 1951 he was appointed professor of physical chemistry at the University of Illinois at Urbana-Champaign. He became professor of chemistry at the California Institute of Technology (Caltech) in Pasadena in 1978.

All living cells depend on the energy generated when electrons pass from one molecule to another. This chemical process, known as electron-transfer reaction, is the driving force behind respiration (the energy producing process of cells), photosynthesis (the conversion of sunlight into energy in plant tissues), and other basic chemical processes. Electron transfers also generate the current in batteries. Before electrons can transfer between molecules, they have to overcome an energy barrier. The size of this barrier determines the speed of the reaction, which can vary widely.

Marcus theorized that the height of the energy barrier could be manipulated by changing the arrangement of atoms in particular molecules or in the surrounding medium. Using this method, he was able to predict the way a reaction would progress, and how quickly. His formula surprised many in the scientific community because it contradicted the long-held belief that large transfers produce quick reactions.