"In developing structural chemistry we have not drawn a line between inorganic and
organic substances, and at first most of our work, covering compounds of all elements,
dealt with organic compounds to only a small extent. However, our methods have been
found to be particularly valuable in the treatment of the complicated problems of
organic chemistry, and we are now devoting the major part of our effort to those problems." Linus Pauling. "Brief Account of Research in Chemistry Supported by Grant from the Rockefeller Foundation." October 24, 1933.
"We are ready to make an intensive attack on the structure of hemoglobin." Linus Pauling. Letter to The Rockefeller Foundation. October 22, 1934.
"The picture is, however, still very far from definite - she suggests various alternatives
and does not make any definite predictions." Linus Pauling. Letter to Warren Weaver. March 6, 1937.
"[Delbrück's] training in physics is good and he attacks biological problems in a
sensible way. He understands their nature, whereas Dr. Wrinch does not." Linus Pauling. Letter to Warren Weaver. February 23, 1938.
"It has been recognized by workers in the field of modern structural chemistry that
the lack of conformity of the cyclol structures with the rules found to hold for simple
molecules makes it very improbable that any protein molecules contain structural elements
of the cyclol type." Linus Pauling Carl G. Niemann. "The structure of proteins." Journal of the American Chemical Society, 61, 1860-1867. 1939.
"I think that this synthesis of antibodies in vitro can be considered pretty important." Linus Pauling. Letter to Warren Weaver. November 18, 1941.
"Although the chances that our work on artificial antibodies will lead to results
of practical value in the immediate future are not great, there does exist some possibility
that the researches will have practical application." Linus Pauling. Letter to Frank Blair Hanson. May 29, 1942.
"It does not seem to us that we should consider going in for the support of immunology
on a broad front at the present time." Frank Blair Hanson. Letter to Linus Pauling. May 7, 1943.
"...I must confess to a good deal of skepticism as to whether it is possible or desirable
to carry over, into peace-time research, many of the elements of organization and
control which properly and inevitably characterize war-time work." Warren Weaver. Letter to Linus Pauling. September 21, 1944.
"It may be emphasized that this explanation for specificity, as due to a complementariness
in structure which permits non-specific intermolecular forces to come into fuller
operation than would be possible for non-complementary structures, is the only explanation
which the present knowledge of molecular structure and intermolecular forces provides." Linus Pauling. "Molecular Structure and Intermolecular Forces." In The Specificity of Serological Reactions, by Karl Landsteiner, 2nd ed. Cambridge, Mass.: Harvard University Press. 1945.
"Even the sense of taste and odor are based upon molecular configuration rather than
upon ordinary chemical properties. A molecule that has the same shape as a camphor
molecule will smell like camphor even though it may be quite unrelated to camphor
chemically." Linus Pauling. "Analogies between Antibodies and Simpler Chemical Substances." Chemical and Engineering News, 24:1064. 1946.
"I think it has really been very much worthwhile for me to get away for this period
of time, under circumstances favorable to my thinking over questions and trying to
find their solution." Linus Pauling. Letter to Robert Corey. March 3, 1948.
"The mechanism of obtaining [immunological specificity] is one of moulding a plastic
material, the coiling chain, into a die or mould, the surface of the antigen molecule.
I believe that the same process of moulding of plastic materials into a configuration
complementary to that of another molecule which serves as a template, is responsible
for all biological specificity. I believe that the genes serve as the templates on
which are moulded the enzymes which are responsible for the chemical characters of
the organism." Linus Pauling. "Molecular Architecture and the Processes of Life," the Twenty-First Sir Jesse Boot
Foundation Lecture. May 28, 1948.
"Proteins hold the key to the whole subject of the molecular basis of biological reactions." Linus Pauling. "Signs of Life." Electronic Medical Digest, 35-36. 1949.
"The difference between our two predicted configurations and the others that have
been described in the literature is that ours are precise, whereas the others are
more or less vague. I feel in a sense that this represents the solution of the problem
of the structure of proteins." Linus Pauling. Letter to Warren Weaver. March 8, 1951.
"In reply to your letter of January 24, 1952, you are informed that your request for
a passport has been carefully considered by the Department. However, a passport of
this Government is not being issued to you since the Department is of the opinion
that your proposed travel would not be in the best interests of the United States." Ruth B. Shipley. Letter to Linus Pauling. February 14, 1952.
"We have been having a lot of fun in our work on the structure of proteins. There
now seems to be pretty general agreement that some of our structures are correct,
although a few people, namely the workers at Courtaulds, are still complaining." Linus Pauling. Letter to Thomas Taylor. July 2, 1952.
"Polypeptide Configuration Conference...Jim Watson will arrive before March & stay.
Invite him, but no money." Linus Pauling. Diary entry. August 1952.
"His attitude toward the patient always dominated his work, and the Clinic for Renal
Diseases at Stanford University held its sessions right in the laboratory, in the
midst of the experiments. On Clinic days, the laboratory was unique and a sight to
be remembered. It was humming with activity. Patients sat all about, watching with
interest the tests, both those which were routine and those which were part of some
special research project, being made in front of their eyes. Then, when Dr. Addis
saw his patient, the information about his condition was up-to-the-minute." Linus Pauling. "Biographical Notes re: Thomas Addis." February 1955.
"The human body contains many other kinds of proteins. Perhaps each human being has
as many as 100,000 different kinds of proteins inside of him....Now the hemoglobin
molecule contains about 10,000 atoms. Nobody knows, even yet, how these atoms are
attached together in space. Nobody knows the complete structure. Yet, during the last
twenty-five years, many pieces of information about the hemoglobin molecule have been
gathered together and I have been especially interested in this." Linus Pauling. National Film Board of Canada interview. 1960.
"In the 1930s already, I began work on the question of the nature of antibodies, antitoxins,
how the human body protects itself against invasion by infection. There is a very
interesting natural mechanism that is involved here. Doctor Karl Landsteiner of the
Rockefeller Institute for Medical Research, who is the man who discovered the blood
groups and made it possible to give transfusions of blood from one human being to
another, is the man who got me interested in this field of immunology." Linus Pauling. National Film Board of Canada interview. 1960.
"I think that we shall be able to get a more thorough understanding of the nature
of disease in general by investigating the molecules that make up the human body,
including the abnormal molecules, and that this understanding will permit...the problem
of disease to be attacked in a more straightforward manner such that new methods of
therapy will be developed." Linus Pauling. National Film Board of Canada interview. 1960.
"Twenty-five years ago I began work on the question of how the four iron atoms in
the hemoglobin molecule are related to the other atoms. My students and I investigated
hemoglobin by measuring its magnetic properties - whether it is attracted by a magnet
or not - and we were successful in finding out something about the nature of the bonds
connecting the four iron atoms - there are four iron atoms in the molecule - with
the other atoms that surround the iron atoms in the hemoglobin molecule. And also
we found out something about the nature of the bonds between the iron atoms and molecules
of oxygen. Hemoglobin in the blood combines with oxygen molecules from the air, in
the lungs...then as the blood flows out to the tissues, the oxygen is carried along.
In the tissues, the hemoglobin molecule gives up the oxygen molecules to the tissues
where it serves to support the oxidation of worn out molecules and to provide energy
to muscle and do the other jobs that are part of the physiological activity of the
human being or other animals. Then the hemoglobin, the blood, flows back to the lungs,
and the hemoglobin again picks up a load of oxygen." Linus Pauling. National Film Board of Canada interview. 1960.
"But after some years, at the end of the war, in connection with my interest in application
of chemistry to medicine, I learned about the disease sickle cell anemia. As soon
as I learned about this disease, the very evening - it was at a dinner in New York
where a medical research committee, of which I was a member, a committee which had
been appointed by President Roosevelt to study medical research in the United States,
was holding a meeting. At this dinner I learned about the disease sickle cell anemia
and immediately I thought, 'Could it be possible that this disease, which seems to
be a disease of the red cell because the red cells in the patients are twisted out
of shape, could really be a disease of the hemoglobin molecule?' Nobody had ever suggested
that there could be molecular diseases before, but this idea popped into my head.
I thought, 'Could it be that these patients manufacture a certain kind of hemoglobin
such that the molecules are sticky and clamp onto one another to form long rods which
then line up side-by-side to form a long, needle-like crystal which, as it grows inside
the red cell, becomes longer than the diameter of the cell and thus twists the red
cell out of shape.' Well, I said to the man who was talking about the disease, Dr.
Castle, 'Has anyone ever suggested that this might be a disease of the hemoglobin
molecule?' And he said not so far as he had ever heard and I said, 'Do you think it
would be alright if I were to look at the hemoglobin from these patients and see?'
And he said 'I don't see why not.' So when I got back to Pasadena, it turned out that
a young M.D., a young medical man wanted to come work with me in chemistry and get
his Ph.D. degree. I said to him - his name is Harvey Itano - I said to him 'Why don't
you work on the hemoglobin that you get from patients with the disease sickle cell
anemia and see whether it is the same as hemoglobin in other humans or its different?'
Nobody had ever found any difference between the hemoglobin of one person and another
before that time. Well Dr. Itano did that, together with the two other young men
in our laboratory - Dr. Singer and Dr. Wells. Pretty soon - it wasn't an easy job,
these proteins are hard substances to work with - but after a while Dr. Itano and
Dr. Singer and Dr. Wells were able to show that if they put a drop of hemoglobin solution
from a patient with this disease in a little trough containing salt solution and applied
an electric field - putting electrodes into this trough - the hemoglobin from the
sickle cell anemia patients would move in one direction in this trough and that from
ordinary individuals would move in the other direction. This was the proof that these
patients have a different kind of hemoglobin; they manufacture a special kind of hemoglobin
molecule which is the cause of their disease. This was the first molecular disease
to be identified, that is the first disease to be shown due to the manufacture by
the patient of an abnormal molecule." Linus Pauling. National Film Board of Canada interview. 1960.
"[Pauling] had already proved himself in the early years to have such an ingrown sense
of the realities of the quantum as applied to chemistry that he did not need to think
about detailed derivations but thought automatically in quantum terms." J. D. Bernal. "The Pattern of Linus Pauling's Work in Relation to Molecular Biology." Structural Chemistry and Molecular Biology: A Volume Dedicated to Linus Pauling By
His Students, Colleagues and Friends (San Francisco: W. H. Freeman). 1968.
"This show, like all of his dazzling performances, delighted the younger students
in the audience. There was no one like Linus in all the world. The combination of
his prodigious mind and his infectious grin was unbeatable. Several fellow professors,
however, watched this performance with mixed feelings....A number of his colleagues
quietly waited for the day when he would fall flat on his face by botching something
important." James D. Watson. The Double Helix 1968.
"It can be said that, by and large, Pauling's idea played an essential role in the
working out of protein structure. But it did far more. It broke away from the limitation
imposed by crystallographers on the integral nature of the turns of a helix. It eventually
led to a new generalization of crystallography that was to have immense repercussions.
It might be said, 'Only a crystallographer could have predicted this development,
but if they were good crystallographers, they would have been bound to reject it.'
Indeed, Pauling's generalization opened the field to a new and much more wide-sweeping
account of semiregular structures that are similar to the helical." J. D. Bernal. "The Pattern of Linus Pauling's Work in Relation to Molecular Biology." Structural Chemistry and Molecular Biology: A Volume Dedicated to Linus Pauling By
His Students, Colleagues and Friends (San Francisco: W. H. Freeman). 1968.
"I found that Landsteiner and I had a much different approach to science: Landsteiner
would ask, 'What do these experimental observations force us to believe about the
nature of the world?' and I would ask, 'What is the most simple, general and intellectually
satisfying picture of the world that encompasses these observations and is not incompatible
with them?'" Linus Pauling. "Fifty Years of Progress in Structural Chemistry and Molecular Biology." Daedalus, 99, 1005. 1970.
"He and I together decided that he should work on the determination of the structure
of some crystals of amino acids and simple peptides. When I say that he and I together
made this decision, I may not be quite right. It is not unlikely that he had already
made the decision, and that he arranged to have me agree with him, in such a way that
I would think that we had made the decision together. I learned later that he was
very good at this..." Linus Pauling. "Robert Brainard Corey." May 3, 1971.
"To my father, nucleic acids were just interesting chemicals, just as sodium chloride
is an interesting chemical." Peter Pauling. "DNA - The Race that Never Was." New Scientist May 31, 1973.
"What I'm telling you now is that I was thinking of the alpha helix in hemoglobin,
and I refrained from saying anything to Max, not because I wanted to keep him from
having significant information, but because there's no use disturbing people about
something unless you feel happy with it yourself." Linus Pauling. Interview with Horace Freeland Judson. December 23, 1975.
"As I lay there in bed, I had an idea about a new way of attacking the problem. Back
in 1937 I had been so impressed by the fact that the amino-acid residues in any position
in the polypeptide chain may be of any of 20 different kinds that the idea that with
respect to folding they might be nearly equivalent had not occurred to me. I accordingly
thought to myself, what would be the consequence of the assumption that all of the
amino-acid residues are structurally equivalent, with respect to the folding of the
polypeptide chain?" Linus Pauling. "The Discovery of the Alpha Helix." September 1982.
"On my return to Pasadena in the fall of 1948 I talked with Professor Corey about
the alpha helix and the gamma helix, and also with Dr. Herman Branson, who had come
for a year as a visiting professor. I asked Dr. Branson to go over my calculations,
and in particular to see if he could find any third helical structure. He reported
that the calculations were all right, and that he could not find a third structure." Linus Pauling. "The Discovery of the Alpha Helix." September 1982.
"...[T]hree ways of folding polypeptide chains have turned out to constitute the most
important secondary structures of all proteins. Dr. Corey, to some extent with my
inspiration, designed molecular models of several different kinds that were of much
use in the later effort to study other methods of folding polypeptide chains. I used
these units to make about 100 different possible structures for folding polypeptide
chains." Linus Pauling. "The Discovery of the Alpha Helix." September 1982.
"[Corey and I] reached the conclusion, as did Crick, that in the alpha-keratin proteins
the alpha helices are twisted together into ropes or cables. This idea essentially
completed our understanding of the alpha-keratin diffraction patterns." Linus Pauling. "The Discovery of the Alpha Helix." September 1982.
"Pauling was a more important figure in molecular biology than is sometimes realized.
Not only did he make certain key discoveries (that sickle cell anemia is a molecular
disease, for example), but he had the correct theoretical approach to these biological
problems." Francis Crick. What Mad Pursuit: A Personal View of Scientific Discovery (New York: Basic Books). 1988.
"Time has shown that, so far, Pauling was right and Delbrück was wrong, as indeed
Delbrück acknowledged in his book, Mind into Matter. Everything we know about molecular biology appears to be explainable in a standard
chemical way." Francis Crick. What Mad Pursuit: A Personal View of Scientific Discovery (New York: Basic Books). 1988.
"During a period of about a decade, beginning in 1926, my principal research effort
was an attack on the problem of the nature of life, which was, I think, successful,
in that the experimental studies carried out by my students and me provided very strong
evidence that the astonishing specificity characteristic of living organisms, such
as an ability to have progeny resembling themselves, is the result of a special interaction
between molecules that have mutually complementary structures. In a world that is
not in thermodynamic equilibrium, such as our earth, parts of which are heated by
sunlight, it is possible for certain chemical reactions to be favored, for example
by the action of enzymes or other catalysts. A molecule or group of molecules that
can catalyze its or their own production is thereby able to prosper. This process,
over a period of four billion years, has led to the existence of human beings. So
we are here, in this wonderful world, with its millions of different kinds of molecules
and crystals, the mountains, the plains and the oceans, and the millions of species
of plants an animals. We have developed a degree of intelligence that permits us to
understand the wonder of the world, and also that has given us the power to destroy
the world and the human race. With Benjamin Franklin I say, 'O that moral Science were in as fair a way of improvement, that men would cease to be wolves to
one another, and that human beings would at length learn what they now improperly
call humanity'." Linus Pauling. "The Meaning of Life." In The Meaning of Life: Reflections in Words and Pictures on Why We Are Here, David Friend and the Editors of Life, eds. (Boston: Little, Brown). 1991.
"Propelled by Dionysian forces far stronger than any of his colleagues', Pauling's
intellectual ambition was reinforced by bold managerial maneuvers that placed him
and Caltech at the forefront of Rockefeller support and of the production of molecular
knowledge." Lily E. Kay. The Molecular Vision of Life: Caltech, The Rockefeller Foundation and the Rise of
the New Biology (New York: Oxford University Press). 1993.
"In suggesting that hydrogen bonds determined the three-dimensional configuration
of proteins - and thus their biological specificity - Pauling and Mirsky enunciated
a fundamental relation between molecular structure and biological function. It was
also one of the cornerstones of Pauling's conception of molecular architecture, a
metaphor and method for explaining life in health and disease, which would lend legitimacy
to the molecular biology enterprise." Lily E. Kay. The Molecular Vision of Life: Caltech, The Rockefeller Foundation and the Rise of
the New Biology (New York: Oxford University Press). 1993.
"Wooden and plastic balls of all colors were designed and made at the laboratories
and shops of the chemistry division, their scales and shapes represented such atoms
as carbon, oxygen and nitrogen as they exist in proteins. They could be added and
subtracted at will, thereby bringing some order to the process of building by trial
and error without a clear blueprint." Lily E. Kay. The Molecular Vision of Life: Caltech, The Rockefeller Foundation and the Rise of
the New Biology (New York: Oxford University Press). 1993.
"During a single year, using his own x-ray equipment, Corey made great strides into
the protein puzzle. He showed that in the crystalline dipeptide diketopiperazine
(a simplified analogue of amino acids), the amide bonds were coplaner, strongly suggesting
the presence of a resonance structure - observations that fit precisely with Pauling's
studies of the amide bond in urea during the early 1930s." Lily E. Kay. The Molecular Vision of Life: Caltech, The Rockefeller Foundation and the Rise of
the New Biology (New York: Oxford University Press). 1993.
"Pauling's model-building approach was novel to both crystallography and biological
research. It became crucial to the investigations of protein structure, allowing
precise visualization of the molecular arrangements and interactions hitherto hidden." Lily E. Kay. The Molecular Vision of Life: Caltech, The Rockefeller Foundation and the Rise of
the New Biology (New York: Oxford University Press). 1993.
"For about forty years I have been thinking of writing a book on the molecular basis
of biological specificity, and I am trying to settle down to writing it. My tentative
title now is The Nature of Life, Including My Life. I felt that biological specificity was the characteristic property of living organisms,
and that it needed to be explained. I think our immunochemical work did that job." Linus Pauling. Letter to Lily Kay. January 1993.
"This was a fortunate arrangement. Not only did Mirsky teach me how to handle proteins
in the laboratory - they are far more delicate than inorganic substances - but he
also gave me a great amount of information about the properties of proteins and especially
about denaturation of proteins." Linus Pauling. "How My Interest in Proteins Developed." January 12, 1993.
"I felt that I knew enough about the structure of polypeptide chains to be able to
determine the structure of alpha-keratin by analyzing Astbury's diffraction photographs
and similar ones made in our own x-ray laboratory, and I spent a good part of the
summer of 1937 in this effort." Linus Pauling. "How My Interest in Proteins Developed." January 12, 1993.
"Todd says that he told Bragg that the amide group was planar, but apparently Bragg
did not understand what he said. I was fortunate in having a good understanding of
two fields, structural chemistry and x-ray diffraction. My recommendation to young
scientists is that they get a thorough knowledge of one field, and also some knowledge
of other fields of science." Linus Pauling. "How My Interest in Proteins Developed." January 12, 1993.
"I don't think it's right, really, to discuss the impact of Linus Pauling on molecular
biology. Rather he was one of the founders of molecular biology. It wasn't that it
existed in some way and he came down and put something on it. He was one of the founders
who got the whole discipline going." Francis Crick. "The Impact of Linus Pauling on Molecular Biology." February 28, 1995.
"While my own work at Caltech had nothing to do with protein structure, Pauling used
to talk to me occasionally about his models and what one could learn from them. In
his lecture, he had talked about spirals. In conversation a few days later, I told
him that for me the word "spiral" referred to a curve in a plane. As his polypeptide
coils were three-dimensional figures, I suggested they were better described as "helices."
Pauling's erudition did not stop at the natural sciences. He answered, quite correctly,
that the words "spiral" and "helix" are practically synonymous and can be used almost
interchangeably, but he thanked me for my suggestion because he preferred "helix"
and declared that he would always use it henceforth. Perhaps he felt that by calling
his structure a helix there would be less risk of confusion with the various other
models that had been proposed earlier. In their 1950 short preliminary communication,
Pauling and Corey wrote exclusively about spirals, but in the series of papers published
the following year the spiral had already given way to the helix. There was no going
back. A few years later we had the DNA double helix, not the DNA double spiral. The
formulation of the α-helix was the first and is still one of the greatest triumphs
of speculative model building in molecular biology, and I am pleased that I helped
to give it its name." Jack Dunitz. "La Primavera." (unpublished manuscript) 2011.
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