Melvin Calvin

Melvin Calvin was born on April 8, 1911 in St. Paul, Minnesota. His parents were Jewish immigrants, his father from Tsarist Lithuania and his mother from Tsarist Georgia. They ran a grocery store in Detroit, Michigan at which Calvin helped out when on break from school. His interest in chemistry was sparked by thinking about how the products that were sold in his parent's store worked. He attended Central High School in Detroit and then studied chemistry at the Michigan College of Mining and Technology where he earned the school's first chemistry bachelors in 1931. He earned his Ph. D. in chemistry in 1935 from the University of Minnesota, completing a thesis on the electron affinity of halogens. Halogens (including fluorine, chlorine, bromine and iodine) are period 17 on the periodic table of elements and have high electron affinities because they have seven electrons in their outer orbitals.

After finishing his Ph.D. he did a  postdoc at the University of Manchester in the lab of Michael Polanyi where he studied phthalocyanines, cyclic organic compounds that form complexes with other atoms and are used as dyes. After two years in Manchester he was offered a lecturer position at the University of California at Berkeley, in 1937, where he was the first non-Berkeley graduate to join the chemistry department in more than a quarter century. Working with Gilbert Lewis he studied the chemistry of the porphyrin the organic nitrogen ring compound found in the heme portion of the hemoglobin molecule. Poryphyrin rings complex with metallic atoms, iron in the case of hemoglobin. Calvin remained at U.C. Berkeley for the rest of his career, where he served as the founding director of the Laboratory of Chemical Biodynamics and as an associate director of the Berkeley Radiation Laboratory.

He was promoted to professor of chemistry in 1947. Calvin is most famous for using radioactive carbon to study the chemical reaction of the carbon fixation, the dark reaction of photosynthesis. In plants the enzyme ribulose-1,5-biphosphate oxygense (RuBisCO) adds carbon dioxide to the five carbon sugar ribulose-1,5-biphosphate, which breaks down into two three carbon phosphogycerate molecules. Carbon fixation is what distinguishes autotrophic plants the other heterotrophic kingdoms of organisms. The cyclic pathway by which carbon dioxide is incorporated by plants is called the Calvin cycle.

For his research on carbon assimilation by plants he was awarded the Nobel Prize in chemistry in 1961. His other honors include election to the National Academy of Science and a postage stamp honoring him in 2008. He served as president of both the American Chemical Society and the American Society of Plant Physiology. He also served as the president of the Pacific Division of the American Society for the Advancement of Science. He served as an adviser to the National Aeronautics and Space Administration regarding the transmission and encounter of pathogens and organic compounds on the Moon and the planets of our solar system. He also served as a presidential scientific adviser. He retired from Berkeley in 1980 but remained doing research until 1996.

He died of a heart attack on January 8, 1997.


References:

Seaborg, Glenn T. and Benson, Andrew A.; "Melvin Calvin: April 8, 1911-January 8, 1997"; Biographical Memoirs Vol 75; National Academy Press; 1998

Melvin Calvin Nobel Biography

Melvin Calvin Wikipedia Entry

Georg Charles de Hevesy

Georg Charles de Hevesy was born on August 1, 1885 in Budapest, Hungary. He was the fifth of eight children of Louis de Hevesy, a public prosecutor and Eugenie (Schossberger) de Hevesy. Beginning in 1903 he attended Budapest University and Berlin Technical University studying chemistry, physics, and mathematics. He earned his doctorate in chemistry at the University of Freiburg im Breisgau in 1908.

He worked for two years at the Institute of Physical Chemistry, Technical University of Switzerland before working for a short spell with Fritz Haber and seeing much of the fundamental work Haber did developing the Haber process to synthesize ammonia. He traveled to Manchester, England in 1910 to study under Ernest Rutherford. Rutherford gave him the task or separating out the radium D from the large amount of lead in a sample of Joachimsthal pitchblende which had been given as a gift by the Austrian government. Of course, try as he might de Hevesy was not able to complete the separation. He was able to use radium D and radium E as a radioactive tracer in investigations of the kinetics of lead and bismuth in plants.

Radium is the heaviest of the alkaline earth metals (group 2 on the periodic table) and is intensely radioactive. The products of radium's decay have been historically known as A, B, C etc. Radium D is now known as lead-210, so of course de Hevesesy was unable to separate the radioactive lead isotope from the non-radioactive lead by normal chemical means, but he was able to use it as a radioactive tracer. Other experiments he performed using radioactive isotopes as tracers included using duterated water (water with radioactive hydrogen) as a tracer to determine the amount of water in the human body and using radioactive phosphorus to determine the rate of deoxyribose nucleic acids in liver and kidney cells. He also was able to determine the lifespan of red blood cells and the doubling time of artificially induced tumors using radioactive tracers.

In 1919 de Hevesy went to work at the Bohr Institute for Theoretical Physics in Copenhagen (he had become friends with Niels Bohr while working in Manchester). Bohr had de Hevesy investigated samples of zircon ore for element number 72, then an empty space on the periodic table. Working with Dirk Coster, he was able to find the missing element and named it hafnium, after the Latin name for Copenhagen, Hafnia.

In 1940, when Germany invaded Denmark, de Hevesy dissolved the Nobel Prizes of Max von Laue and James Franck in aqua regia, to prevent the Germans from stealing them, and placed the solution on a shelf in the Bohr institute. Afterwards he was forced to flee Denmark to Sweden, because of his Jewish ancestry. After the war he returned to find the solution still on the shelf where he had left it and precipitated the gold out. He gave the gold to the Nobel Society, which recast the prizes. In 1943 de Hevesy was awarded the Nobel Prize "for his work on the use of isotopes as tracers in the study of chemical processes".

De Hevesy died on July 5, 1966.

References:

Feld, Michael, de Roo, M.;History of Nuclear Medicine in Europe; Schattauer Verlag; 2006

George de Hevesy Nobel Biography

Geroge de Hevesy Wikipedia Entry