Sam Ruben

Samuel Ruben was born Charles Rubenstein in San Francisco, California, November 5, 1913, the son of Herschel and Frieda Penn Rubenstein – the name was officially shortened to Ruben in 1930. Young Sam developed a friendship with neighbor Jack Dempsey and became involved with a local boys' boxing club and later, when the family moved across the Bay to Berkeley, he was a successful basketball player at Berkeley High School (Berkeley, California). After achieving his B.S. in Chemistry at the University of California, Berkeley, he continued his studies there and was awarded a Ph.D. in Physical Chemistry in May 1938. He was immediately appointed Instructor in the Chemistry Department, and became an Assistant Professor in 1941.

Sam and colleague Martin Kamen, a University of Chicago Ph.D. and researcher in chemistry and nuclear physics working under Ernest O. Lawrence at the Berkeley Radiation Laboratory, set out to elucidate the path of carbon in photosynthesis by incorporating the short-lived radioactive isotope Carbon-11 (11CO2) in their many experiments between 1938 and 1942. Aided by the concepts and collaboration of C. B. van Niel, at Stanford University’s Hopkins Marine Station, it became clear to them that reduction of CO2 can occur in the dark and may involve processes similar to bacterial systems. This interpretation challenged the century-old Adolf von Baeyer theory of photochemical reduction of CO2 adsorbed on chlorophyll which had guided decades of effort by Richard Willstätter, A. Stoll, and many others in vain searches for formaldehyde.

In hundreds of experiments with Carbon-11 produced from deuterons and Boron-10 by Martin Kamen in the Radiation Laboratory’s 37-inch cyclotron, Ruben and Kamen, with collaborators from botany, microbiology, physiology and organic chemistry, pursued the path of carbon dioxide in plants, algae, and bacteria. Their results, confused by absorption of the products on proteinaceous residues, initially failed to reveal the path of carbon in photosynthesis but succeeded in exciting the interest of scientists world-wide in the search and revelation of metabolic processes, beginning a revolution in biochemistry and medicine.

Ruben’s experiments using 'heavy water', H2O18, to yield 18O2 gas had shown that the oxygen gas produced in photosynthesis comes from water. With nuclear physicists' tenuous prediction of a "long lived radioactive carbon isotope,” Ruben and Kamen pursued several routes that could lead to identification of the Carbon-14 isotope. After several failed attempts, Martin Kamen collected the results of a 120-hour cyclotron bombardment of graphite and trudged in the rain with it to the “Rat House,” adjacent both to the Chemistry Department and to the cyclotron, and Sam Ruben's desk.  At 8 AM, February 27, 1940, Sam Ruben demonstrated unequivocally the radioactivity was from Carbon-14.

The weak energy of Carbon-14 made measurement tedious. So tedious that no tracer experiments with C-14 were done until 1942 when Sam Ruben gave all his barium carbonate-C14 to young Chemistry Department faculty member Andrew Benson who began his long series of 14CO2 fixation experiments to determine the path of carbon in photosynthesis. Only in 1949 did chemist Willard Libby use it to invent radiocarbon dating.

Ruben's recruitment for research in the World War II wartime effort led him to interest in the mechanism of phosgene as a poisonous gas. With C-11 phosgene (11COCl2) prepared by Benson, they studied the combination of phosgene with lung proteins. Following Benson's departure from Berkeley in July 1943, Ruben died September 28, 1943 after a disastrous exposure to phosgene in a laboratory accident the preceding day.

Sam Ruben married Helena Collins West, a fellow chemistry student, during his final semester as an undergraduate at UC Berkeley, on September 28, 1935. They had three children, Dana West Ruben (born November 11, 1938), George Collins Ruben (born April 29, 1941, and Connie Mae Ruben Fatt (born June 18, 1943).

The discovery of Carbon-14, the most useful of all artificial isotopes and consequent major advances in biology and medicine, failed to result in a deserved Nobel Prize for Ruben and Kamen.