Linus Pauling

Pauling's graduation photo from Oregon State University, 1922

In his first semester, Pauling registered for two courses in chemistry, two in mathematics, mechanical drawing, introduction to mining and use of explosives, modern English prose, gymnastics and military drill.[30] He was active in campus life and founded the school's chapter of the Delta Upsilon fraternity.[31] After his second year, he planned to take a job in Portland to help support his mother. The college offered him a position teaching quantitative analysis, a course he had just finished taking himself. He worked forty hours a week in the laboratory and classroom and earned $100 a month (equivalent to $1,300 in 2019), enabling him to continue his studies.[32]

In his last two years at school, Pauling became aware of the work of Gilbert N. Lewis and Irving Langmuir on the electronic structure of atoms and their bonding to form molecules.[32] He decided to focus his research on how the physical and chemical properties of substances are related to the structure of the atoms of which they are composed, becoming one of the founders of the new science of quantum chemistry.

Engineering professor Samuel Graf selected Pauling to be his teaching assistant in a mechanics and materials course.[33][34][35] During the winter of his senior year, Pauling taught a chemistry course for home economics majors. It was in one of these classes that Pauling met his future wife, Ava Helen Miller.[34]^:41[36][37][38]

In 1922, Pauling graduated from Oregon State University[13] (known then as Oregon Agricultural College) with a degree in chemical engineering. He went on to graduate school at the California Institute of Technology (Caltech) in Pasadena, California, under the guidance of Roscoe Dickinson and Richard Tolman.[2] His graduate research involved the use of X-ray diffraction to determine the structure of crystals. He published seven papers on the crystal structure of minerals while he was at Caltech. He received his PhD in physical chemistry and mathematical physics,[1] summa cum laude, in 1925.[39]

Linus Pauling with an inset of his Nobel Prize in 1955

In the late 1920s, Pauling began publishing papers on the nature of the chemical bond. Between 1937 and 1938, he took a position as George Fischer Baker Non-Resident Lecturer in Chemistry at Cornell University. While at Cornell, he delivered a series of nineteen lectures[55] and completed the bulk of his famous textbook The Nature of the Chemical Bond.[56][57]^:Preface It is based primarily on his work in this area that he received the Nobel Prize in Chemistry in 1954 "for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances".[8] Pauling's book has been considered "chemistry's most influential book of this century and its effective bible".[58] In the 30 years after its first edition was published in 1939, the book was cited more than 16,000 times. Even today, many modern scientific papers and articles in important journals cite this work, more than seventy years after the first publication.[59]

Part of Pauling's work on the nature of the chemical bond led to his introduction of the concept of orbital hybridization.[60] While it is normal to think of the electrons in an atom as being described by orbitals of types such as s and p, it turns out that in describing the bonding in molecules, it is better to construct functions that partake of some of the properties of each. Thus the one 2s and three 2p orbitals in a carbon atom can be (mathematically) 'mixed' or combined to make four equivalent orbitals (called sp³ hybrid orbitals), which would be the appropriate orbitals to describe carbon compounds such as methane, or the 2s orbital may be combined with two of the 2p orbitals to make three equivalent orbitals (called sp² hybrid orbitals), with the remaining 2p orbital unhybridized, which would be the appropriate orbitals to describe certain unsaturated carbon compounds such as ethylene.[57]^:111–120 Other hybridization schemes are also found in other types of molecules. Another area which he explored was the relationship between ionic bonding, where electrons are transferred between atoms, and covalent bonding, where electrons are shared between atoms on an equal basis. Pauling showed that these were merely extremes, and that for most actual cases of bonding, the quantum-mechanical wave function for a polar molecule AB is a combination of wave functions for covalent and ionic molecules.[44]^:66 Here Pauling's electronegativity concept is particularly useful; the electronegativity difference between a pair of atoms will be the surest predictor of the degree of ionicity of the bond.[61]

The third of the topics that Pauling attacked under the overall heading of "the nature of the chemical bond" was the accounting of the structure of aromatic hydrocarbons, particularly the prototype, benzene.[62] The best description of benzene had been made by the German chemist Friedrich Kekulé. He had treated it as a rapid interconversion between two structures, each with alternating single and double bonds, but with the double bonds of one structure in the locations where the single bonds were in the other. Pauling showed that a proper description based on quantum mechanics was an intermediate structure which was a blend of each. The structure was a superposition of structures rather than a rapid interconversion between them. The name "resonance" was later applied to this phenomenon.[63] In a sense, this phenomenon resembles those of hybridization and also polar bonding, both described above, because all three phenomena involve combining more than one electronic structure to achieve an intermediate result.

In 1929, Pauling published five rules which help to predict and explain crystal structures of ionic compounds.[64][44] These rules concern (1) the ratio of cation radius to anion radius, (2) the electrostatic bond strength, (3) the sharing of polyhedron corners, edges and faces, (4) crystals containing different cations, and (5) the rule of parsimony.

Pauling in 1941

An alpha helix in ultra-high-resolution electron density contours, with O atoms in red, N atoms in blue, and hydrogen bonds as green dotted lines (PDB file 2NRL, 17–32).

In the mid-1930s, Pauling, strongly influenced by the biologically oriented funding priorities of the Rockefeller Foundation's Warren Weaver, decided to strike out into new areas of interest.[65] Although Pauling's early interest had focused almost exclusively on inorganic molecular structures, he had occasionally thought about molecules of biological importance, in part because of Caltech's growing strength in biology. Pauling interacted with such great biologists as Thomas Hunt Morgan, Theodosius Dobzhanski, Calvin Bridges and Alfred Sturtevant.[66] His early work in this area included studies of the structure of hemoglobin with his student Charles D. Coryell. He demonstrated that the hemoglobin molecule changes structure when it gains or loses an oxygen atom.[66] As a result of this observation, he decided to conduct a more thorough study of protein structure in general. He returned to his earlier use of X-ray diffraction analysis. But protein structures were far less amenable to this technique than the crystalline minerals of his former work. The best X-ray pictures of proteins in the 1930s had been made by the British crystallographer William Astbury, but when Pauling tried, in 1937, to account for Astbury's observations quantum mechanically, he could not.[67]

It took eleven years for Pauling to explain the problem: his mathematical analysis was correct, but Astbury's pictures were taken in such a way that the protein molecules were tilted from their expected positions. Pauling had formulated a model for the structure of hemoglobin in which atoms were arranged in a helical pattern, and applied this idea to proteins in general.

In 1951, based on the structures of amino acids and peptides and the planar nature of the peptide bond, Pauling, Robert Corey and Herman Branson correctly proposed the alpha helix and beta sheet as the primary structural motifs in protein secondary structure.[68][69] This work exemplified Pauling's ability to think unconventionally; central to the structure was the unorthodox assumption that one turn of the helix may well contain a non-integer number of amino acid residues; for the alpha helix it is 3.7 amino acid residues per turn.

Pauling then proposed that deoxyribonucleic acid (DNA) was a triple helix;[70][71] his model contained several basic mistakes, including a proposal of neutral phosphate groups, an idea that conflicted with the acidity of DNA. Sir Lawrence Bragg had been disappointed that Pauling had won the race to find the alpha helix structure of proteins. Bragg's team had made a fundamental error in making their models of protein by not recognizing the planar nature of the peptide bond. When it was learned at the Cavendish Laboratory that Pauling was working on molecular models of the structure of DNA, James Watson and Francis Crick were allowed to make a molecular model of DNA. They later benefited from unpublished data from Maurice Wilkins and Rosalind Franklin at King's College which showed evidence for a helix and planar base stacking along the helix axis. Early in 1953 Watson and Crick proposed a correct structure for the DNA double helix. Pauling later cited several reasons to explain how he had been misled about the structure of DNA, among them misleading density data and the lack of high quality X-ray diffraction photographs. During the time Pauling was researching the problem, Rosalind Franklin in England was creating the world's best images. They were key to Watson's and Crick's success. Pauling did not see them before devising his mistaken DNA structure, although his assistant Robert Corey did see at least some of them, while taking Pauling's place at a summer 1952 protein conference in England. Pauling had been prevented from attending because his passport was withheld by the State Department on suspicion that he had Communist sympathies. This led to the legend that Pauling missed the structure of DNA because of the politics of the day (this was at the start of the McCarthy period in the United States). Politics did not play a critical role. Not only did Corey see the images at the time, but Pauling himself regained his passport within a few weeks and toured English laboratories well before writing his DNA paper. He had ample opportunity to visit Franklin's lab and see her work, but chose not to.[47]^:414–415

Pauling also studied enzyme reactions and was among the first to point out that enzymes bring about reactions by stabilizing the transition state of the reaction, a view which is central to understanding their mechanism of action.[72] He was also among the first scientists to postulate that the binding of antibodies to antigens would be due to a complementarity between their structures.[73] Along the same lines, with the physicist turned biologist Max Delbrück, he wrote an early paper arguing that DNA replication was likely to be due to complementarity, rather than similarity, as suggested by a few researchers. This was made clear in the model of the structure of DNA that Watson and Crick discovered.[74]

Pauling in 1948

In November 1949, Pauling, Harvey Itano, S. J. Singer and Ibert Wells published "Sickle Cell Anemia, a Molecular Disease"[75] in the journal Science. It was the first proof of a human disease caused by an abnormal protein, and sickle cell anemia became the first disease understood at the molecular level. Using electrophoresis, they demonstrated that individuals with sickle cell disease have a modified form of hemoglobin in their red blood cells, and that individuals with sickle cell trait have both the normal and abnormal forms of hemoglobin. This was the first demonstration causally linking an abnormal protein to a disease, and also the first demonstration that Mendelian inheritance determines the specific physical properties of proteins, not simply their presence or absence – the dawn of molecular genetics.[76]

His success with sickle cell anemia led Pauling to speculate that a number of other diseases, including mental illnesses such as schizophrenia, might result from flawed genetics. As chairman of the Division of Chemistry and Chemical Engineering and director of the Gates and Crellin Chemical Laboratories, he encouraged the hiring of researchers with a chemical-biomedical approach to mental illness, a direction not always popular with established Caltech chemists.[77]^:2

In 1951, Pauling gave a lecture entitled "Molecular Medicine".[78] In the late 1950s, Pauling studied the role of enzymes in brain function, believing that mental illness may be partly caused by enzyme dysfunction.

On September 16, 1952, Pauling opened a new research notebook with the words "I have decided to attack the problem of the structure of nuclei." On October 15, 1965, Pauling published his Close-Packed Spheron Model of the atomic nucleus in two well respected journals, Science and the Proceedings of the National Academy of Sciences.[79][80] For nearly three decades, until his death in 1994, Pauling published numerous papers on his spheron cluster model.[79][81][82][83][84][85]

The basic idea behind Pauling's spheron model is that a nucleus can be viewed as a set of "clusters of nucleons". The basic nucleon clusters include the deuteron [np], helion [pnp], and triton [npn]. Even–even nuclei are described as being composed of clusters of alpha particles, as has often been done for light nuclei.[86] Pauling attempted to derive the shell structure of nuclei from pure geometrical considerations related to Platonic solids rather than starting from an independent particle model as in the usual shell model. In an interview given in 1990 Pauling commented on his model:[87]

Now recently, I have been trying to determine detailed structures of atomic nuclei by analyzing the ground state and excited state vibrational bends, as observed experimentally. From reading the physics literature, Physical Review Letters and other journals, I know that many physicists are interested in atomic nuclei, but none of them, so far as I have been able to discover, has been attacking the problem in the same way that I attack it. So I just move along at my own speed, making calculations ...

Beckman D2 Oxygen Analyzer, ca.1950

Pauling had been practically apolitical until World War II. At the beginning of the Manhattan Project, Robert Oppenheimer invited him to be in charge of the Chemistry division of the project. However, he declined, not wanting to uproot his family.[88]

Beckman Model 735 Dissolved O2 Analyzer, later model based on Pauling's design, 1968

Beckman Model D Oxygen Meter, based on Pauling's design, with infant incubator, 1959

Pauling did, however, work on research for the military. He was a principal investigator on 14 OSRD contracts.[89] The National Defense Research Committee called a meeting on October 3, 1940, wanting an instrument that could reliably measure oxygen content in a mixture of gases, so that they could measure oxygen conditions in submarines and airplanes. In response Pauling designed the Pauling oxygen meter, which was developed and manufactured by Arnold O. Beckman, Inc. After the war, Beckman adapted the oxygen analyzers for use in incubators for premature babies.[90]^:180–186[91]

In 1942, Pauling successfully submitted a proposal on "The Chemical Treatment of Protein Solutions in the Attempt to Find a Substitute for Human Serum for Transfusions". His project group, which included J.B. Koepfli and Dan Campbell, developed a possible replacement for human blood plasma in transfusions: polyoxy gelatin (Oxypolygelatin).[92][93]

Other wartime projects with more direct military applications included work on explosives, rocket propellants and the patent for an armor-piercing shell. In October 1948 Pauling was awarded a Presidential Medal for Merit by President Harry S. Truman. The citation credits him for his "imaginative mind", "brilliant success", and "exceptionally meritorious conduct in the performance of outstanding services.[94][95][96] In 1949, he served as president of the American Chemical Society.[97]

The aftermath of the Manhattan Project and his wife Ava's pacifism changed Pauling's life profoundly, and he became a peace activist.

In June 1945, a "May-Johnson Bill" began[98][99][100] that would become the Atomic Energy Act of 1946 (signed August 1, 1946). In November 1945, Pauling spoke to the Independent Citizens Committee of the Arts, Sciences and Professions (ICCASP) on atomic weapons; shortly after, wife Ava and he accepted membership.[101] On January 21, 1946, the group met to discuss academic freedom, during which Pauling said, "There is, of course, always a threat to academic freedom – as there is to the other aspects of the freedom and rights of the individual, in the continued attacks which are made on this freedom, these rights, by the selfish, the overly ambitious, the misguided, the unscrupulous, who seek to oppress the great body of mankind in order that they themselves may profit – and we must always be on the alert against this threat, and must fight it with vigor when it becomes dangerous."[101]

In 1946, he joined the Emergency Committee of Atomic Scientists, chaired by Albert Einstein.[102] Its mission was to warn the public of the dangers associated with the development of nuclear weapons.

His political activism prompted the US State Department to deny him a passport in 1952, when he was invited to speak at a scientific conference in London.[103][104] In a speech before the US Senate on June 6 of the same year, Senator Wayne Morse publicly denounced the action of the State Department, and urged the Passport Division to reverse its decision. Pauling and his wife Ava were then issued a "limited passport" to attend the aforementioned conference in England.[105][106] His full passport was restored in 1954, shortly before the ceremony in Stockholm where he received his first Nobel Prize.

Joining Einstein, Bertrand Russell and eight other leading scientists and intellectuals, he signed the Russell-Einstein Manifesto issued July 9, 1955.[107] He also supported the Mainau Declaration of July 15, 1955, signed by 52 Nobel Prize laureates.[108]

In May 1957, working with Washington University in St. Louis professor Barry Commoner, Pauling began to circulate a petition among scientists to stop nuclear testing.[109] On January 15, 1958, Pauling and his wife presented a petition to United Nations Secretary General Dag Hammarskjöld calling for an end to the testing of nuclear weapons. It was signed by 11,021 scientists representing fifty countries.[110][111]

In February 1958, Pauling participated in a publicly televised debate with the atomic physicist Edward Teller about the actual probability of fallout causing mutations.[112] Later in 1958, Pauling published No more war!, in which he not only called for an end to the testing of nuclear weapons but also an end to war itself . He proposed that a World Peace Research Organization be set up as part of the United Nations to "attack the problem of preserving the peace".[8]

Pauling also supported the work of the St. Louis Citizen's Committee for Nuclear Information (CNI).[109] This group, headed by Barry Commoner, Eric Reiss, M. W. Friedlander and John Fowler, organized a longitudinal study to measure radioactive strontium-90 in the baby teeth of children across North America. The "Baby Tooth Survey," published by Dr. Louise Reiss, demonstrated conclusively in 1961 that above-ground nuclear testing posed significant public health risks in the form of radioactive fallout spread primarily via milk from cows that had ingested contaminated grass.[113][114][115] The Committee for Nuclear Information is frequently credited for its significant contribution to supporting the test ban,[116] as is the ground-breaking research conducted by Dr. Reiss and the "Baby Tooth Survey".[117]

Public pressure and the frightening results of the CNI research subsequently led to a moratorium on above-ground nuclear weapons testing, followed by the Partial Test Ban Treaty, signed in 1963 by John F. Kennedy and Nikita Khrushchev. On the day that the treaty went into force, October 10, 1963, the Nobel Prize Committee awarded Pauling the Nobel Peace Prize for 1962. (No prize had previously been awarded for that year.)[118] They described him as "Linus Carl Pauling, who ever since 1946 has campaigned ceaselessly, not only against nuclear weapons tests, not only against the spread of these armaments, not only against their very use, but against all warfare as a means of solving international conflicts."[119] Pauling himself acknowledged his wife Ava's deep involvement in peace work, and regretted that she was not awarded the Nobel Peace Prize with him.[120]

Pauling's beret on display at the Nobel Prize Museum

Many of Pauling's critics, including scientists who appreciated the contributions that he had made in chemistry, disagreed with his political positions and saw him as a naïve spokesman for Soviet communism. In 1960, he was ordered to appear before the Senate Internal Security Subcommittee,[121] which termed him "the number one scientific name in virtually every major activity of the Communist peace offensive in this country."[122] A headline in Life magazine characterized his 1962 Nobel Prize as "A Weird Insult from Norway".[123][124]

Pauling was a frequent target of the National Review magazine. In an article entitled "The Collaborators" in the magazine's July 17, 1962 issue, Pauling was referred to not only as a collaborator, but as a "fellow traveler" of proponents of Soviet-style communism. In 1965, Pauling sued the magazine, its publisher William Rusher, and its editor William F. Buckley, Jr for $1 million. He lost both his libel suits and the 1968 appeal.[125][126][127][128]

His peace activism, his frequent travels, and his enthusiastic expansion into chemical-biomedical research all aroused opposition at Caltech. In 1958, the Caltech Board of Trustees demanded that Pauling step down as chairman of the Chemistry and Chemical Engineering Division.[77]^:2 Although he had retained tenure as a full professor, Pauling chose to resign from Caltech after he received the Nobel peace prize money. He spent the next three years at the Center for the Study of Democratic Institutions (1963–1967).[21] In 1967, he moved to the University of California at San Diego, but remained there only briefly, leaving in 1969 in part because of political tensions with the Reagan-era board of regents.[77]^:3 From 1969 to 1974, he accepted a position as Professor of Chemistry at Stanford University.[42]

During the 1960s, President Lyndon Johnson's policy of increasing America's involvement in the Vietnam War caused an anti-war movement that the Paulings joined with enthusiasm. Pauling denounced the war as unnecessary and unconstitutional. He made speeches, signed protest letters and communicated personally with the North Vietnamese leader, Ho Chi Minh, and gave the lengthy written response to President Johnson. His efforts were ignored by the American government.[129]

Pauling was awarded the International Lenin Peace Prize by the USSR in 1970.[122][130] He continued his peace activism in the following years. He and his wife Ava helped to found the International League of Humanists in 1974.[131] He was president of the scientific advisory board of the World Union for Protection of Life and also one of the signatories of the Dubrovnik-Philadelphia Statement of 1974/1976.[132] Linus Carl Pauling was an honorary president and member of the International Academy of Science, Munich until the end of his life.[133]

Pauling supported a limited form of eugenics by suggesting that human carriers of defective genes be given a compulsory visible mark – such as a forehead tattoo – to discourage potential mates with the same defect, in order to reduce the number of babies with diseases such as sickle cell anemia.[134][135]

Pauling's book, How to Live Longer and Feel Better, advocated very high intake of Vitamin C.[136]

In 1941, at age 40, Pauling was diagnosed with Bright's disease, a renal disease. Following the recommendations of Thomas Addis, who actively recruited Ava Helen Pauling as "nutritionist, cook, and eventually as deputy 'doctor'", Pauling believed he was able to control the disease with Addis's then-unusual low-protein salt-free diet and vitamin supplements.[137] Thus Pauling's initial – and intensely personal – exposure to the idea of treating disease with vitamin supplements was positive.

In 1965, Pauling read Niacin Therapy in Psychiatry by Abram Hoffer and theorized vitamins might have important biochemical effects unrelated to their prevention of associated deficiency diseases.[138] In 1968, Pauling published a brief paper in Science entitled "Orthomolecular psychiatry",[139] giving a name to the popular but controversial megavitamin therapy movement of the 1970s, and advocating that "orthomolecular therapy, the provision for the individual person of the optimum concentrations of important normal constituents of the brain, may be the preferred treatment for many mentally ill patients." Pauling coined the term "orthomolecular" to refer to the practice of varying the concentration of substances normally present in the body to prevent and treat disease. His ideas formed the basis of orthomolecular medicine, which is not generally practiced by conventional medical professionals and has been strongly criticized.[140][141]

In 1973, with Arthur B. Robinson and another colleague, Pauling founded the Institute of Orthomolecular Medicine in Menlo Park, California, which was soon renamed the Linus Pauling Institute of Science and Medicine. Pauling directed research on vitamin C, but also continued his theoretical work in chemistry and physics until his death. In his last years, he became especially interested in the possible role of vitamin C in preventing atherosclerosis and published three case reports on the use of lysine and vitamin C to relieve angina pectoris. During the 1990s, Pauling put forward a comprehensive plan for the treatment of heart disease using lysine and vitamin C. In 1996, a website was created expounding Pauling's treatment which it referred to as Pauling Therapy. Proponents of Pauling Therapy believe that heart disease can be treated and even cured using only lysine and Vitamin C and without drugs or heart operations.[142]

Pauling's work on vitamin C in his later years generated much controversy. He was first introduced to the concept of high-dose vitamin C by biochemist Irwin Stone in 1966. After becoming convinced of its worth, Pauling took 3 grams of vitamin C every day to prevent colds.[13] Excited by his own perceived results, he researched the clinical literature and published Vitamin C and the Common Cold in 1970. He began a long clinical collaboration with the British cancer surgeon Ewan Cameron in 1971 on the use of intravenous and oral vitamin C as cancer therapy for terminal patients.[143] Cameron and Pauling wrote many technical papers and a popular book, Cancer and Vitamin C, that discussed their observations. Pauling made vitamin C popular with the public[144] and eventually published two studies of a group of 100 allegedly terminal patients that claimed vitamin C increased survival by as much as four times compared to untreated patients.[145][146]

A re-evaluation of the claims in 1982 found that the patient groups were not actually comparable, with the vitamin C group being less sick on entry to the study, and judged to be "terminal" much earlier than the comparison group.[147] Later clinical trials conducted by the Mayo Clinic also concluded that high-dose (10,000 mg) vitamin C was no better than placebo at treating cancer and that there was no benefit to high-dose vitamin C.[148][149][150] The failure of the clinical trials to demonstrate any benefit resulted in the conclusion that vitamin C was not effective in treating cancer; the medical establishment concluded that his claims that vitamin C could prevent colds or treat cancer were quackery.[13][151] Pauling denounced the conclusions of these studies and handling of the final study as "fraud and deliberate misrepresentation",[152][153] and criticized the studies for using oral, rather than intravenous vitamin C[154] (which was the dosing method used for the first ten days of Pauling's original study[151]). Pauling also criticised the Mayo clinic studies because the controls were taking vitamin C during the trial, and because the duration of the treatment with vitamin C was short; Pauling advocated continued high-dose vitamin C for the rest of the cancer patient's life whereas the Mayo clinic patients in the second trial were treated with vitamin C for a median of 2.5 months.[155] The results were publicly debated at length with considerable acrimony between Pauling and Cameron, and Moertel (the lead author of the Mayo Clinic studies), with accusations of misconduct and scientific incompetence on both sides.

Ultimately the negative findings of the Mayo Clinic studies ended general interest in vitamin C as a treatment for cancer.[153] Despite this, Pauling continued to promote vitamin C for treating cancer and the common cold, working with The Institutes for the Achievement of Human Potential to use vitamin C in the treatment of brain-injured children.[156] He later collaborated with the Canadian physician Abram Hoffer on a micronutrient regime, including high-dose vitamin C, as adjunctive cancer therapy.[157] A 2009 review also noted differences between the studies, such as the Mayo clinic not using intravenous Vitamin C, and suggested further studies into the role of vitamin C when given intravenously.[158]

Pauling died of prostate cancer on August 19, 1994, at 19:20 at home in Big Sur, California.[165] He was 93 years old.[166] A grave marker for Pauling was placed in Oswego Pioneer Cemetery in Lake Oswego, Oregon by his sister Pauline, but Pauling's ashes, along with those of his wife, were not buried there until 2005.[167]

Pauling's discoveries led to decisive contributions in a diverse array of areas including around 350 publications in the fields of quantum mechanics, inorganic chemistry, organic chemistry, protein structure, molecular biology, and medicine.[168][169]

His work on chemical bonding marks him as one of the founders of modern quantum chemistry.[10] The Nature of the Chemical Bond was the standard work for many years,[170] and concepts like hybridization and electronegativity remain part of standard chemistry textbooks. While his Valence bond approach fell short of accounting quantitatively for some of the characteristics of molecules, such as the color of organometallic complexes, and would later be eclipsed by the molecular orbital theory of Robert Mulliken, Valence Bond Theory still competes, in its modern form, with Molecular Orbital Theory and density functional theory (DFT) as a way of describing the chemical phenomena.[171] Pauling's work on crystal structure contributed significantly to the prediction and elucidation of the structures of complex minerals and compounds.[34]^:80–81 His discovery of the alpha helix and beta sheet is a fundamental foundation for the study of protein structure.[69]

Francis Crick acknowledged Pauling as the "father of molecular biology".[10][172] His discovery of sickle cell anemia as a "molecular disease" opened the way toward examining genetically acquired mutations at a molecular level.[76]

Pauling's 1951 publication with Robert B. Corey and H. R. Branson, "The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain," was a key early finding in the then newly emerging field of molecular biology. This publication was honored by a Citation for Chemical Breakthrough Award from the Division of History of Chemistry of the American Chemical Society presented to the Department of Chemistry, Caltech, in 2017.[173][174]

Oregon State University completed construction of the $77 million, 100,000-square-foot (9,300 m²) Linus Pauling Science Center in the late 2000s, now housing a bulk of Oregon State's chemistry classrooms, labs, and instruments.[175]

On March 6, 2008, the United States Postal Service released a 41 cent stamp honoring Pauling designed by artist Victor Stabin.[176][177] His description reads: "A remarkably versatile scientist, structural chemist Linus Pauling (1901–1994) won the 1954 Nobel Prize in Chemistry for determining the nature of the chemical bond linking atoms into molecules. His work in establishing the field of molecular biology; his studies of hemoglobin led to the classification of sickle cell anemia as a molecular disease."[76] The other scientists on this sheet of stamps included Gerty Cori, biochemist, Edwin Hubble, astronomer, and John Bardeen, physicist.[177]

California Governor Arnold Schwarzenegger and First Lady Maria Shriver announced on May 28, 2008 that Pauling would be inducted into the California Hall of Fame, located at The California Museum for History, Women and the Arts. The induction ceremony took place December 15, 2008. Pauling's son was asked to accept the honor in his place.[178]

By proclamation of Gov. John Kitzhaber in the state of Oregon, February 28 has been named "Linus Pauling Day".[179] The Linus Pauling Institute still exists, but moved in 1996 from Palo Alto, California, to Corvallis, Oregon, where it is part of the Linus Pauling Science Center at Oregon State University.[180][181][182] The Valley Library Special Collections at Oregon State University contain the Ava Helen and Linus Pauling Papers, including digitized versions of Pauling's forty-six research notebooks.[179]

In 1986, Caltech commemorated Linus Pauling with a Symposium and Lectureship.[183] The Pauling Lecture series at Caltech began in 1989 with a lecture by Pauling himself. The Caltech Chemistry Department renamed room 22 of Gates Hall the Linus Pauling Lecture Hall, since Linus spent so much time there.[184]

Other places named after Pauling include Pauling Street in Foothill Ranch, California;[185] Linus Pauling Drive in Hercules, California; Linus and Ava Helen Pauling Hall at Soka University of America in Aliso Viejo, California;[186] Linus Pauling Middle School in Corvallis, Oregon;[187] and Pauling Field, a small airfield located in Condon, Oregon, where Pauling spent his youth.[188] There is a psychedelic rock band in Houston, Texas, named The Linus Pauling Quartet.[189]

The asteroid 4674 Pauling in the inner asteroid belt, discovered by Eleanor F. Helin, was named after Linus Pauling in 1991, on his 90th birthday.[190]

Linus Torvalds, developer of the Linux kernel, is named after Pauling.[191]

Nobel laureate Peter Agre has said that Linus Pauling inspired him.[192]

In 2010, Pacific Northwest National Laboratory named its distinguished postdoctoral program in his honor, as the Linus Pauling Distinguished Postdoctoral Fellowship Program.

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