Linus Pauling

Linus Pauling

American chemist who applied quantum mechanics to the study of molecular structures, particularly in connection with chemical bonding. Pauling received the Nobel Prize for Chemistry in 1954 and the Nobel Prize for Peace in 1962 (the latter in recognition of his efforts on behalf of the international control of nuclear weapons and his campaigns against nuclear testing).

Pauling received his B.S. in chemical engineering at Oregon State Agricultural College (now Oregon State University), Corvallis, in 1922, then became a graduate assistant at the California Institute of Technology, Pasadena, where he took his Ph.D. in physical chemistry in 1925. For two years he was a postdoctoral fellow in Europe, working in the laboratories of such noted scientists as Arnold Sommerfeld in Munich, Niels Bohr in Copenhagen, Erwin Schrodinger in Zurich, and Sir William Henry Bragg in London. He returned to the California Institute of Technology as assistant professor of chemistry in 1927, becoming full professor in 1931 and serving as director of the Gates and Crellin Laboratories of Chemistry between 1936 and 1958.

Scientific achievements.
Pauling's chemical work, for which he received his first Nobel Prize, dealt with the many aspects of molecular structure, ranging from simple molecules to proteins. He was among the first to apply the principles of quantum mechanics to the structure of molecules and effectively utilized X-ray diffraction (the alteration of the straight course of X rays by the interference of an atom or group of atoms), electron diffraction (interference with the course of electrons by atoms), magnetic effects, and the heat involved in forming chemical compounds for the calculation of interatomic distances and the angles between chemical bonds. He was successful in relating the distances and angles between chemical bonds to molecular characteristics and to interaction between molecules.
In order to account for the equivalency of the four bonds around the carbon atom, he introduced the concept of hybrid orbitals, in which electron orbits are moved from their original positions by mutual repulsion. Pauling also recognized the presence of hybrid orbitals in the coordination of ions or groups of ions in a definite geometric arrangement about a central ion. His theory of directed (positive and negative) valence (the capacity of an atom to combine with other atoms) was an outgrowth of his early work, as was the concept of the partial ionic character of covalent bonds--i.e., atoms sharing electrons. His empirical concept of electronegativity, the power of attraction for electrons in a covalent bond, was useful in further clarification of these problems. In the case of compounds whose molecules cannot be represented unambiguously by a single structure, he introduced the concept of resonance hybrids whereby the true structure of the molecule is regarded as an intermediate state between two or more depictable structures. The resonance theory came under heavy but unsuccessful attack in the U.S.S.R. in 1951 when doctrinaire scientists of the Communist Party argued that it conflicted with dialectical materialist principles. The ideas on bonding were developed serially in his numerous journal articles during his early career and were consolidated in his book The Nature of the Chemical Bond and the Structure of Molecules and Crystals (1939), which grew out of lectures he gave in 1937 and 1938. The textbook proved to be one of the most influential of the century.

In 1934 Pauling began to apply his knowledge of molecular structure to the complex molecules of living tissues, particularly in connection with proteins. His studies of the magnetic susceptibility (the ease with which something can be magnetized) of the hemoglobin (the red protein in the red cells of the blood) molecule during oxygenation inaugurated a succession of studies that led to a theory of native proteins (active proteins as found in living organisms), denatured proteins (ones that through heat or chemical action have broken some of their bonds), and coagulated (solidified) proteins. He became interested in proteins involved in immunological reactions and in 1940, with a German-born biologist, Max Delbruck, developed a concept of molecular complementarity in antibody-antigen reactions (in which the production of antibodies is stimulated in an organism when foreign substances called antigens are introduced). He recognized the importance of hydrogen bonding in protein structure and in interactions between macromolecules (extremely large molecules usually built from repeating groups of smaller molecules). His work with an American chemist, Robert B. Corey, on the structure of amino acids and polypeptides (the chief components of proteins) led him to recognize that certain proteins have helical structures.

Late in the 1940s Pauling became interested in sickle-cell anemia when he learned that the red blood corpuscles show their abnormal crescent shape only in venous blood. Intuitively, he reasoned that the cause of the cell deformity must lie in a genetic defect associated with hemoglobin formation. His studies showed that the sickling effect was nullified by the presence of oxygen in the arterial blood.

Pauling also developed a molecular model for the explanation of anesthesia that was made public in 1961, introduced ideas toward the understanding of memory processes, and in 1965 postulated a theory of the atomic nucleus that had certain advantages over other models. His scientific career was characterized by the application of intuitive guesses aided by a phenomenal memory of chemical facts. Pauling referred to this as the stochastic method (from the Greek "apt to divine the truth by conjecture").

Campaign for nuclear weapons disarmament.
Following the development of nuclear weapons, Pauling became deeply concerned about the possible hazards of exposure to radiation associated with weapons testing. He expressed his view in his book No More War! (1958). In January 1958 he brought to the United Nations a petition signed by 11,021 scientists from all over the world urging an end to nuclear weapons tests. In 1963 he left the California Institute of Technology to become a staff member of the Center for the Study of Democratic Institutions at Santa Barbara, where he largely devoted himself to the study of problems of peace and war. No official reason was given for the award of the Peace Prize for 1962 to Pauling in 1963, but it is widely assumed that he received it for his efforts in behalf of the Nuclear Test-Ban Treaty that was concluded in the same year. His pacifist views estranged him from many scientists with whom he had been closely associated during the years of World War II, when he had served as a civilian with the Office of Scientific Research and Development. Though he was equally opposed to nuclear testing by the United States and the Soviet Union, his loyalty to the United States was questioned in some conservative political circles.

Later years.
In 1969 Pauling resigned a position he had held for two years with the University of California, San Diego, in protest against the educational policies of the governor of California. He joined the chemistry department of Stanford University in California, where he was named professor emeritus in 1974. In 1973 he founded the Linus Pauling Institute of Science and Medicine to study the prevention and treatment of illness through the intake of optimum doses of vitamins and minerals, especially the daily intake of megadoses (6 to 18 grams) of vitamin C. His theories on vitamin C and nutrition therapy, which he promoted in his books Vitamin C and the Common Cold (1970), Cancer and Vitamin C (1979), and How to Live Longer and Feel Better (1986), provoked much controversy in the medical community.
In addition to winning two Nobel Prizes, Pauling was widely honoured in scientific and pacifist circles. He held guest appointments in many other universities, both at home and abroad. His success as a scientist was based on his capacity for quick insight into new problems, his ability to recognize interrelationships, and the courage to put forward unorthodox ideas. While his concepts were not always correct, they always stimulated discussion and investigation.

Barbara Marinacci (ed.), Linus Pauling in His Own Words (1995), is a selection of his writings and interviews on various topics. Biographies include Anthony Serafini, Linus Pauling: A Man and His Science (1989); Ted Goertzel and Ben Goertzel, Linus Pauling: A Life in Science and Politics (1995); and Thomas Hager, Linus Pauling (1995).

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