PAULING, LINUS
(1901–1994)

Linus Pauling was a chemist, peace campaigner, and double Nobel Laureate who played a central role in two great unifying projects of twentieth-century science.

Born in Oregon, U.S.A., in 1901, Pauling worked his way through college, receiving a BS in chemistry from Oregon Agricultural College in 1922. There he read papers on valence by physical chemists G. N. Lewis and Irving Langmuir, sparking his interest in the theory of chemical structure and bonding. He moved to California Institute of Technology (Caltech) for doctoral work on X-ray studies of inorganic crystal structures and had published twelve papers by the time he graduated in 1925. In 1926 he traveled to Europe on a Guggenheim postdoctoral fellowship, visiting Munich and other centers of the new quantum mechanics. On his return from Europe, Pauling resumed his work on X-ray crystallography, developing what he later called his chemical intuition about possible crystal structures. He also set about applying quantum mechanics to chemistry. Simultaneously with physicist John Clarke Slater, he developed physicists Walter Heitler and Fritz London's 1927 work on the hydrogen molecule to explain the structure of polyatomic molecules. The resulting valence-bond approach to molecular quantum mechanics, which modeled observed molecular structures as resonance hybrids of classical structures, faced competition from the molecular-orbital approach. The early success of the valence-bond approach is largely due to Pauling's advocacy, his developing intuitive visual representations to accompany his theoretical work, and his publication of the enormously influential Nature of the Chemical Bond (1939), which brought together his many contributions to structural chemistry.

Despite this central role in unifying the sciences, Pauling was no reductionist. He regarded his application of quantum mechanics to chemistry as a synthesis of physical theory with independent principles of chemical structure.

Pauling's second great unifying project was the chemical understanding of biologically important molecules. From the 1930s onward, he applied the X-ray and electron-diffraction methods, used earlier on inorganic crystals, to the structure of peptides and proteins, including hemoglobin. Subsequently, Pauling studied the molecular basis of the immune system and identified the first molecular disease—sickle-cell anemia. Pauling's work was also influential in James Watson and Francis Crick's proposal of a double-helix structure for DNA in 1953, though Pauling denied having participated in a race to discover the structure of the molecule.

Pauling was a controversialist in science and in politics: Though he publicly defended Japanese internees, he supported U.S. entry in to the Second World War and was active scientifically in the war effort, earning a Presidential Medal of Merit in 1948. During the cold war, however, he became increasingly involved in campaigning for nuclear disarmament and for a test-ban treaty on both political and scientific grounds. This, and his defense of blacklisted scientists, led to interest from the Federal Bureau of Investigation and the denial of a passport in the early 1950s. A passport was forthcoming, however, when Pauling was awarded the 1954 Nobel Prize in Chemistry for his work on the chemical bond and his contributions to the understanding of the structure of proteins. His political campaigning also earned him a second Nobel Prize (in Peace) in 1962.

Pauling left Caltech in 1964, partly as a result of his high political profile, spending the next decade at the Santa Barbara Center for the Study of Democratic Institutions (1964–1967), the University of California at San Diego (1967–1969), and Stanford University (1969–1973). On retirement from there, he cofounded the Linus Pauling Institute of Science and Medicine in Palo Alto, California, from where he continued his popular, though scientifically controversial, advocacy of high doses of vitamin C to improve health and to slow down aging. He remained active in research until nearly the end of his life.

See also Chemistry, Philosophy of; Peace, War, and Philosophy; Quantum Mechanics; Social and Political Philosophy.

Bibliography

Hager, Thomas. Force of Nature: The Life of Linus Pauling. New York: Simon and Schuster, 1995.

Mason, Stephen. "The Science and Humanism of Linus Pauling (1901–1994)." Chemical Society Reviews (1997): 29–39.

Pauling, Linus. The Nature of the Chemical Bond and the Structure of Molecules and Crystals; An Introduction to Modern Structural Chemistry. 3rd ed. Ithaca, NY: Cornell University Press, 1960.

Pauling, Linus. "Fifty Years of Progress in Structural Chemistry and Molecular Biology." Daedalus 99 (4) (Fall 1970): 988–1014.

Robin Findlay Hendry (2005)