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Linus Pauling
(1901-1994)
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).
Education.
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.
BIBLIOGRAPHY.
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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