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Linus Pauling
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Linus Pauling

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Linus Pauling

Linus Pauling

Linus Carl Pauling ( PAW -ling ; February 28, 1901 – August 19, 1994) was an American chemist and peace activist. He published more than 1,200 papers and…

Linus Carl Pauling ( PAW-ling; February 28, 1901 – August 19, 1994) was a prominent American chemist and peace advocate. His extensive bibliography comprises over 1,200 publications, including papers and books, with approximately 850 focusing on scientific subjects. Scientific American recognized him as one of history's twenty most significant scientists. Pauling received the Nobel Prize in Chemistry in 1954 for his groundbreaking scientific contributions. Subsequently, in 1962, he was honored with the Nobel Peace Prize for his dedicated peace activism. He stands among only five individuals who have been recipients of multiple Nobel Prizes. Notably, he is the sole recipient of two unshared Nobel Prizes and one of only two individuals, alongside Marie Curie, to be awarded Nobel Prizes in distinct disciplines.

Linus Carl Pauling ( PAW-ling; February 28, 1901 – August 19, 1994) was an American chemist and peace activist. He published more than 1,200 papers and books, of which about 850 dealt with scientific topics. Scientific American called him one of the 20 greatest scientists of all time. For his scientific work, Pauling was awarded the Nobel Prize in Chemistry in 1954. For his peace activism, he was awarded the Nobel Peace Prize in 1962. He is one of five people to have won more than one Nobel Prize. Of these, he is the only person to have been awarded two unshared Nobel Prizes, and one of two people to be awarded Nobel Prizes in different fields, the other being Marie Curie.

Pauling is recognized as a foundational figure in both quantum chemistry and molecular biology. His significant contributions to chemical bonding theory encompass the introduction of orbital hybridization and the development of the first precise electronegativity scale for elements. Furthermore, Pauling investigated the structures of biological molecules, elucidating the critical roles of the alpha helix and beta sheet in protein secondary structure. His methodology integrated techniques and findings from X-ray crystallography, molecular model building, and quantum chemistry. Pauling's pioneering discoveries provided inspiration for the research conducted by James Watson, Francis Crick, Rosalind Franklin, and Maurice Wilkins concerning DNA structure, thereby enabling geneticists to decipher the genetic code across all organisms.

During his later life, Pauling advocated for nuclear disarmament, alongside orthomolecular medicine, megavitamin therapy, and dietary supplements, particularly ascorbic acid (Vitamin C). However, his propositions regarding the therapeutic efficacy of high-dose vitamins have not achieved widespread acceptance within the mainstream scientific community. He was married to Ava Helen Pauling, an American human rights activist.

Formative Years and Academic Development

Linus Carl Pauling was born on February 28, 1901, in Portland, Oregon, as the eldest child of Herman Henry William Pauling (1876–1910) and Lucy Isabelle "Belle" Darling (1881–1926). His given name, "Linus Carl," honored his maternal grandfather, Linus, and his paternal grandfather, Carl. His lineage encompassed German and English heritage.

Following the birth of his sister Pauline in 1902, Pauling's parents opted to relocate from Portland in pursuit of more economical and expansive housing than their single-room apartment. Lucy resided with her husband's parents in Oswego until Herman relocated the family to Salem, where he was briefly employed as a traveling salesman for the Skidmore Drug Company. Less than a year after Lucile's birth in 1904, Herman Pauling moved his family to Oswego, Oregon, establishing his own drugstore there. In 1905, the family relocated again to Condon, Oregon. By 1906, Herman Pauling began experiencing recurrent abdominal pain. His death from a perforated ulcer occurred on June 11, 1910, leaving Lucy responsible for their three children: Linus, Lucile, and Pauline.

Pauling credited his initial fascination with chemistry to the captivating experiments performed by his friend, Lloyd A. Jeffress, who possessed a modest chemistry laboratory kit. He subsequently articulated his profound interest, stating: "I was simply entranced by chemical phenomena, by the reactions in which substances, often with strikingly different properties, appear; and I hoped to "

During his high school years, Pauling performed chemistry experiments using equipment and materials salvaged from a disused steel plant. Collaborating with an older friend, Lloyd Simon, Pauling established "Palmon Laboratories" in Simon's basement. They attempted to offer butterfat sampling services to local dairies at competitive rates; however, the dairymen's reluctance to entrust such a task to two young boys led to the venture's ultimate failure.

By the age of 15, Pauling, then a high school senior, had accumulated sufficient credits for admission to Oregon State University (OSU), which was then known as Oregon Agricultural College. Despite having met most requirements, he lacked two American history courses necessary for his high school diploma and requested permission from the principal to complete these concurrently during the spring semester. This request was denied, leading him to depart Washington High School in June without receiving his diploma. Forty-five years later, following his receipt of two Nobel Prizes, the school conferred upon him an honorary diploma.

Pauling undertook various employments to finance his prospective university education, including part-time work at a grocery store for US$8 per week (equivalent to US$240 in 2025). His mother facilitated an interview with Mr. Schwietzerhoff, the owner of several manufacturing plants in Portland, who employed him as an apprentice machinist at a salary of US$40 per month (equivalent to US$1,180 in 2025), which subsequently increased to US$50 per month. Pauling also established a photography laboratory with two friends. In September 1917, Pauling gained admission to Oregon State University. He promptly resigned from the machinist's position and apprised his mother, who harbored skepticism regarding the value of higher education, of his intentions.

Higher education

In his initial semester, Pauling enrolled in two chemistry courses, two mathematics courses, mechanical drawing, an introduction to mining and the use of explosives, modern English prose, gymnastics, and military drill. His roommate was Lloyd Jeffress, a longtime friend. Pauling actively participated in campus activities and established the university's chapter of the Delta Upsilon fraternity. Following his second year, he intended to secure employment in Portland to contribute to his mother's financial support. The college extended an offer for a teaching position in quantitative analysis, a subject he had recently completed as a student. He dedicated forty hours weekly to laboratory and classroom instruction, earning US$100 per month (equivalent to US$1,600 in 2025), thereby facilitating the continuation of his academic pursuits.

During his final two years of undergraduate studies, Pauling encountered the research of Gilbert N. Lewis and Irving Langmuir concerning the electronic structure of atoms and their bonding to form molecules. He resolved to concentrate his research on elucidating the relationship between the physical and chemical properties of substances and the atomic structures comprising them, thereby emerging as a foundational figure in the nascent field of quantum chemistry.

Engineering professor Samuel Graf (1887–1966) appointed Pauling as his teaching assistant in a course on mechanics and materials. During the winter semester of his final year, Pauling instructed a chemistry course specifically designed for home economics students. Within one of these instructional settings, Pauling encountered his future spouse, Ava Helen Miller.

In 1922, Pauling earned a degree in chemical engineering. He subsequently pursued graduate studies at the California Institute of Technology (Caltech) in Pasadena, California, mentored by Roscoe Dickinson and Richard Tolman. His graduate research focused on employing X-ray diffraction for the structural determination of crystals. During his tenure at Caltech, he authored seven publications concerning the crystal structures of minerals. In 1925, he was awarded his Ph.D. in physical chemistry and mathematical physics, graduating summa cum laude.

Career

In 1926, Pauling received a Guggenheim Fellowship, enabling him to travel to Europe for studies with German physicist Arnold Sommerfeld in Munich, Danish physicist Niels Bohr in Copenhagen, and Austrian physicist Erwin Schrödinger in Zürich. These three individuals were distinguished authorities in the nascent domain of quantum mechanics and related physical disciplines. Pauling developed an interest in the potential applications of quantum mechanics within his selected area of inquiry: the electronic structure of atoms and molecules. In Zürich, he also encountered one of the pioneering quantum mechanical analyses of hydrogen molecule bonding, conducted by Walter Heitler and Fritz London. Pauling dedicated the entirety of his two-year European sojourn to this endeavor, resolving to establish it as the central theme of his subsequent research. He emerged as a seminal figure in quantum chemistry and a trailblazer in applying quantum theory to molecular structure.

In 1927, Pauling commenced a new appointment as an assistant professor of theoretical chemistry at Caltech. He initiated a highly prolific five-year period in his academic career, characterized by continued X-ray crystallographic investigations and the execution of quantum mechanical calculations on atoms and molecules. During this time, he authored approximately fifty publications and formulated the five principles subsequently recognized as Pauling's rules. By 1929, he was advanced to associate professor, and by 1930, he achieved full professorship. In 1931, the American Chemical Society conferred upon Pauling the Langmuir Prize, acknowledging his exceptional contributions to pure science by an individual aged 30 or younger. The following year, Pauling released a seminal publication, which he considered his most significant, introducing the concept of atomic orbital hybridization and providing an analysis of carbon's tetravalency.

At Caltech, Pauling developed a close association with Robert Oppenheimer, a theoretical physicist from the University of California, Berkeley, who annually visited Caltech for portions of his research and teaching commitments. Pauling himself maintained an affiliation with Berkeley, serving as a visiting lecturer in physics and chemistry between 1929 and 1934. Oppenheimer notably presented Pauling with a remarkable personal mineral collection. The collaborators intended to undertake a joint investigation into the nature of the chemical bond, with Oppenheimer contributing the mathematical framework and Pauling interpreting the findings. However, their professional and personal rapport deteriorated following Oppenheimer's attempt to pursue Pauling's wife, Ava Helen. During Pauling's absence at work, Oppenheimer visited their residence and abruptly proposed that Ava Helen accompany him on a rendezvous in Mexico. She unequivocally declined the proposition and subsequently informed Pauling of the occurrence. Consequently, Pauling promptly terminated his association with Oppenheimer.

In the summer of 1930, Pauling undertook a subsequent European journey, during which he acquired knowledge of gas-phase electron diffraction from Herman Francis Mark. Upon his return, he constructed an electron diffraction apparatus at Caltech, collaborating with his student Lawrence Olin Brockway, and employed it for the investigation of molecular structures across numerous chemical compounds.

Pauling pioneered the concept of electronegativity in 1932. By leveraging diverse molecular properties, including bond dissociation energies and molecular dipole moments, he devised a scale and assigned corresponding numerical values to the majority of elements — the Pauling Electronegativity Scale — . This scale proves instrumental in forecasting the character of interatomic bonds within molecular structures.

In 1936, Pauling was advanced to the chairmanship of the Division of Chemistry and Chemical Engineering at Caltech, concurrently assuming the directorship of the Gates and Crellin Laboratories of Chemistry. He maintained both roles until 1958. Additionally, Pauling spent a year in 1948 at the University of Oxford, serving as the George Eastman Visiting Professor and a Fellow of Balliol.

The Nature of the Chemical Bond

In the late 1920s, Pauling initiated the publication of scholarly articles concerning the nature of the chemical bond. Between 1937 and 1938, he accepted an appointment as the George Fischer Baker Non-Resident Lecturer in Chemistry at Cornell University. During his tenure at Cornell, he presented a series of nineteen lectures and substantially completed his renowned textbook The Nature of the Chemical Bond. His contributions in this domain were the primary basis for his receipt of the 1954 Nobel Prize in Chemistry, awarded "for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances". Pauling's treatise has been acclaimed as "chemistry's most influential book of this century and its effective bible". Within three decades of its initial publication in 1939, the book garnered over 16,000 citations. Remarkably, even in contemporary scholarship, numerous scientific papers and articles in prominent journals continue to cite this work, more than seventy years subsequent to its inaugural release.

Pauling's investigations into the nature of the chemical bond culminated in the introduction of the orbital hybridization concept. Although atomic electrons are conventionally characterized by s and p orbital types, molecular bonding descriptions are enhanced by constructing functions that integrate properties from each. For instance, a carbon atom's single 2s orbital and three 2p orbitals can be mathematically combined to form four equivalent sp§45§ hybrid orbitals, suitable for describing carbon compounds like methane. Alternatively, the 2s orbital can combine with two 2p orbitals to yield three equivalent sp§67§ hybrid orbitals, leaving one 2p orbital unhybridized, which is appropriate for certain unsaturated carbon compounds such as ethylene. Diverse hybridization schemes are observed across various molecular structures. He also investigated the interplay between ionic bonding, characterized by electron transfer, and covalent bonding, defined by equal electron sharing between atoms. Pauling demonstrated that these represented mere extremes, and that in most practical bonding scenarios, the quantum-mechanical wave function for a polar AB molecule constitutes a composite of covalent and ionic molecular wave functions. Pauling's electronegativity concept proves especially valuable in this context, as the electronegativity difference between two atoms reliably predicts the bond's degree of ionicity.

Under the overarching theme of "the nature of the chemical bond," Pauling addressed the structural elucidation of aromatic hydrocarbons, with a particular focus on benzene as the prototype. The most comprehensive description of benzene had previously been provided by the German chemist Friedrich Kekulé. Kekulé proposed a rapid interconversion between two structures, each featuring alternating single and double bonds, where the double bonds of one structure occupied the positions of the single bonds in the other. Pauling, however, demonstrated that a quantum-mechanically sound description involved an intermediate structure, representing a blend of these two forms. This structure was characterized as a superposition of forms, rather than a dynamic interconversion. This phenomenon subsequently acquired the designation "resonance." Conceptually, this phenomenon parallels hybridization and polar bonding, both previously discussed, as all three entail the combination of multiple electronic structures to yield an intermediate outcome.

Ionic Crystal Structures

In 1929, Pauling promulgated five rules designed to predict and elucidate the crystal structures of ionic compounds. These principles address (1) the cation-to-anion radius ratio, (2) electrostatic bond strength, (3) the sharing of polyhedron corners, edges, and faces, (4) crystals incorporating diverse cations, and (5) the principle of parsimony.

Biological Molecules

During the mid-1930s, Pauling, significantly swayed by the Rockefeller Foundation's Warren Weaver and his biologically focused funding directives, opted to venture into novel research domains. While Pauling's initial research predominantly centered on inorganic molecular structures, he had intermittently considered biologically significant molecules, partly due to Caltech's expanding prominence in biology. Pauling engaged with eminent biologists including Thomas Hunt Morgan, Theodosius Dobzhanski, Calvin Bridges, and Alfred Sturtevant. His foundational contributions in this field encompassed structural investigations of hemoglobin, conducted with his student Charles D. Coryell. He demonstrated that the hemoglobin molecule undergoes structural alterations upon the acquisition or release of an oxygen molecule. This observation prompted him to undertake a more comprehensive examination of protein structure broadly. He reverted to his prior application of X-ray diffraction analysis. However, protein structures proved considerably less amenable to this technique compared to the crystalline minerals he had previously studied. The most advanced X-ray images of proteins in the 1930s were produced by the British crystallographer William Astbury; nevertheless, when Pauling attempted to quantum mechanically explain Astbury's findings in 1937, he was unsuccessful.

Pauling required eleven years to elucidate a particular problem: his mathematical analysis proved accurate, but Astbury's photographic representations depicted protein molecules tilted from their anticipated orientations. Pauling had previously developed a helical model for hemoglobin's structure, a concept he subsequently generalized to proteins.

In 1951, Pauling, Robert Corey, and Herman Branson accurately identified the alpha helix and beta sheet as the fundamental structural motifs within protein secondary structure. Their proposal was grounded in the known structures of amino acids and peptides, alongside the recognized planar geometry of the peptide bond. This research underscored Pauling's capacity for unconventional thought, notably his unorthodox premise that a helical turn could encompass a non-integer number of amino acid residues, specifically 3.7 residues per turn for the alpha helix.

Subsequently, Pauling posited that deoxyribonucleic acid (DNA) adopted a triple helix conformation; however, his model contained fundamental inaccuracies, including the assertion of neutral phosphate groups, which contradicted DNA's known acidity. Sir Lawrence Bragg expressed disappointment that Pauling had successfully elucidated the alpha helix structure of proteins, a race Bragg's team lost due to a critical error in their protein models—their failure to acknowledge the planar nature of the peptide bond. Upon learning of Pauling's work on molecular models of DNA structure, James Watson and Francis Crick at the Cavendish Laboratory were authorized to construct their own DNA model. They subsequently leveraged unpublished data from Maurice Wilkins and Rosalind Franklin at King's College, which provided evidence for a helical structure and planar base stacking along the helix axis. In early 1953, Watson and Crick successfully proposed the correct double helix structure for DNA. Pauling later attributed his misdirection regarding DNA's structure to factors such as misleading density data and the absence of high-quality X-ray diffraction photographs, characterizing this episode as "the biggest disappointment in his life."

Concurrently with Pauling's research into the DNA problem, Rosalind Franklin in England was generating superior X-ray diffraction images, which proved instrumental to Watson and Crick's eventual success. Pauling did not personally view these images prior to formulating his erroneous DNA structure, although his assistant, Robert Corey, observed at least some of them while representing Pauling at a protein conference in England during the summer of 1952. Pauling's inability to attend was due to the State Department's withholding of his passport, based on suspicions of Communist sympathies—an event occurring at the outset of the McCarthy period in the United States. This circumstance fostered a popular narrative that political interference prevented Pauling from discovering the DNA structure. However, this narrative is inaccurate; Corey had access to the images, and Pauling himself regained his passport within weeks, subsequently touring English laboratories well before authoring his DNA paper. He possessed ample opportunity to Despite these events, Pauling chose to transcend them, expressing gratitude for his prior scientific achievements.

Pauling additionally investigated enzyme reactions, being among the first to articulate that enzymes facilitate reactions by stabilizing the transition state, a concept fundamental to comprehending their operational mechanisms. He was also a pioneer in postulating that the interaction between antibodies and antigens arises from structural complementarity. Extending this principle, he co-authored an early paper with physicist-turned-biologist Max Delbrück, contending that DNA replication likely proceeds via complementarity rather than similarity, a notion proposed by some contemporary researchers. This concept was subsequently elucidated by the DNA structure model discovered by Watson and Crick.

Molecular genetics.

In November 1949, Pauling, Harvey Itano, S. J. Singer, and Ibert Wells published "Sickle Cell Anemia, a Molecular Disease" in the journal Science. This publication provided the initial evidence of a human disease caused by an abnormal protein, establishing sickle cell anemia as the first disease understood at the molecular level. While Maud Menten and collaborators had previously demonstrated the electrophoretic distinction of variant hemoglobin forms, this publication marked the first causal link. Their electrophoretic analysis revealed that individuals with sickle cell disease possess an altered hemoglobin variant in their red blood cells, whereas those with sickle cell trait exhibit both the wild-type and aberrant forms of hemoglobin. This represented the inaugural demonstration causally connecting an aberrant protein to a pathological condition, and furthermore, the first instance illustrating that Mendelian inheritance dictates the precise physical characteristics of proteins, rather than merely their existence or absence, thereby inaugurating the field of molecular genetics.

Pauling's groundbreaking work on sickle cell anemia prompted him to hypothesize that numerous other diseases, including mental illnesses such as schizophrenia, might stem from genetic predispositions or defects. In his capacities as Chairman of the Division of Chemistry and Chemical Engineering and Director of the Gates and Crellin Chemical Laboratories, he advocated for the recruitment of scientists employing a chemical-biomedical methodology to investigate mental disorders. This interdisciplinary orientation, however, occasionally met with resistance from established chemists at Caltech.

In 1951, Pauling delivered a lecture titled "Molecular Medicine." During the late 1950s, he investigated the enzymatic contributions to cerebral function, positing that enzymatic dysregulation could partially underlie mental illnesses. In the 1960s, driven by his concern regarding the ramifications of nuclear weaponry, he explored the evolutionary significance of mutations and, in collaboration with his student Emile Zuckerkandl, advanced the concept of the molecular evolutionary clock, which postulates a consistent rate of mutation accumulation in proteins and DNA over geological timescales.

Structure of the Atomic Nucleus

On September 16, 1952, Pauling initiated a new research notebook, articulating his intent with the statement: "I have decided to attack the problem of the structure of nuclei." On October 15, 1965, Pauling disclosed his Close-Packed Spheron Model of the atomic nucleus in two esteemed journals, Science and the Proceedings of the National Academy of Sciences. Over the subsequent three decades, until his demise in 1994, Pauling extensively published on his spheron cluster model.

Pauling's spheron model fundamentally posits that an atomic nucleus comprises "clusters of nucleons." These fundamental nucleon clusters encompass the deuteron [np], helion [pnp], and triton [npn]. Even-even nuclei are characterized as aggregates of alpha particles, a common representation for lighter nuclei. Pauling endeavored to deduce the nuclear shell structure through purely geometrical principles associated with Platonic solids, diverging from the independent particle model typically employed in conventional shell theory. During a 1990 interview, Pauling offered the following commentary on his model:

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 ...

Activism

Wartime Work

Prior to World War II, Pauling maintained a largely apolitical stance. Early in the Manhattan Project, Robert Oppenheimer extended an invitation for Pauling to lead its Chemistry division. Pauling declined this offer, citing a reluctance to relocate his family.

Nevertheless, Pauling contributed to military research efforts. He served as a principal investigator for 14 contracts with the Office of Scientific Research and Development (OSRD). On October 3, 1940, the National Defense Research Committee convened a meeting to solicit an instrument capable of precisely quantifying oxygen concentration in gas mixtures, essential for monitoring conditions within submarines and aircraft. In response, Pauling devised the Pauling oxygen meter, subsequently developed and produced by Arnold O. Beckman, Inc. Post-war, Beckman modified these oxygen analyzers for application in incubators designed for premature infants.

In 1942, Pauling successfully proposed research titled "The Chemical Treatment of Protein Solutions in the Attempt to Find a Substitute for Human Serum for Transfusions." His project group, which included Joseph B. Koepfli and Dan H. Campbell, subsequently developed polyoxy gelatin (Oxypolygelatin) as a potential replacement for human blood plasma in transfusions.

Additional wartime endeavors with more direct military applications encompassed work on explosives, rocket propellants, and the patenting of an armor-piercing shell. In October 1948, Pauling, alongside Lee A. DuBridge, William A. Fowler, Max Mason, and Bruce H. Sage, was awarded a Presidential Medal for Merit by President Harry S. Truman. The accompanying citation lauded his "imaginative mind," "brilliant success," and "exceptionally meritorious conduct in the performance of outstanding services." In 1949, he assumed the presidency of the American Chemical Society.

Nuclear Activism

The profound impact of the Manhattan Project's aftermath, coupled with his wife Ava's pacifist convictions, significantly transformed Pauling's life, leading him to become a prominent peace activist.

In June 1945, the "May-Johnson Bill" was introduced, which would later be enacted as the Atomic Energy Act of 1946 on August 1, 1946. Pauling addressed the Independent Citizens Committee of the Arts, Sciences and Professions (ICCASP) on atomic weapons in November 1945, and shortly thereafter, he and his wife Ava accepted membership. During a January 21, 1946, meeting of the group focused on academic freedom, Pauling articulated, "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."

In 1946, he joined the Emergency Committee of Atomic Scientists, chaired by Albert Einstein, whose mission was to inform the public about the inherent dangers of nuclear weapons development.

His burgeoning political activism led the US State Department to deny him a passport in 1952, preventing his attendance at a scientific conference in London. On June 6 of the same year, Senator Wayne Morse publicly condemned the State Department's action before the US Senate, urging the Passport Division to reverse its decision. Consequently, Pauling and his wife Ava were issued a "limited passport" to attend the conference. His full passport was reinstated in 1954, shortly before the ceremony in Stockholm where he received his first Nobel Prize.

Joining Albert Einstein, Bertrand Russell, and eight other leading scientists and intellectuals, Pauling signed the Russell-Einstein Manifesto, issued on July 9, 1955. He also endorsed the Mainau Declaration of July 15, 1955, which was signed by 52 Nobel Prize laureates.

In May 1957, in collaboration with Washington University in St. Louis professor Barry Commoner, Pauling initiated a petition among scientists advocating for the cessation of nuclear testing. On January 15, 1958, Pauling and his wife presented this petition to United Nations Secretary General Dag Hammarskjöld, calling for an end to nuclear weapons tests. The petition garnered signatures from 11,021 scientists representing fifty countries.

In February 1958, Pauling engaged in a publicly televised debate with atomic physicist Edward Teller concerning the actual probability of fallout inducing mutations. Later that year, Pauling published No more war!, a work that not only urged an end to nuclear weapons testing but also advocated for the abolition of war itself. He proposed the establishment of a World Peace Research Organization as part of the United Nations to "attack the problem of preserving the peace."

Pauling extended his support to the St. Louis Citizen's Committee for Nuclear Information (CNI). This organization, led by Barry Commoner, Eric Reiss, M. W. Friedlander, and John Fowler, initiated a longitudinal study to quantify radioactive strontium-90 levels in the deciduous teeth of children throughout North America. The "Baby Tooth Survey," authored by Louise Reiss and published in 1961, definitively established that atmospheric nuclear testing presented substantial public health hazards due to radioactive fallout, primarily disseminated through milk from cows consuming contaminated forage. The Committee for Nuclear Information, along with the seminal research by Reiss and the "Baby Tooth Survey," is widely recognized for its pivotal role in advocating for a test ban.

The combination of public outcry and the alarming findings from the CNI research culminated in a moratorium on atmospheric nuclear weapons testing, succeeded by the Partial Test Ban Treaty. This treaty was signed in 1963 by John F. Kennedy and Nikita Khrushchev. On October 10, 1963, the day the treaty became effective, the Nobel Prize Committee conferred the 1962 Nobel Peace Prize upon Pauling, noting that no award had been issued for that year previously. The committee lauded 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." Pauling personally recognized his wife Ava's profound engagement in peace advocacy and expressed regret that she did not share the Nobel Peace Prize with him.

Political Criticism

Numerous detractors of Pauling, even scientists who acknowledged his significant contributions to chemistry, diverged from his political stances, perceiving him as an unsophisticated advocate for Soviet communism. In 1960, he received a summons to testify before the Senate Internal Security Subcommittee, which labeled him "the number one scientific name in virtually every major activity of the Communist peace offensive in this country." A prominent headline in Life magazine famously described his 1962 Nobel Prize as "A Weird Insult from Norway."

Pauling frequently became the subject of criticism in National Review magazine. An article titled "The Collaborators," published in the July 17, 1962, issue of the magazine, characterized Pauling not merely as a collaborator but also as a "fellow traveler" aligned with proponents of Soviet-style communism. In 1963, Pauling initiated a lawsuit seeking $1 million against the magazine, its publisher William Rusher, and its editor William F. Buckley, Jr. He was unsuccessful in both his initial libel suits and the subsequent 1968 appeal, a different outcome from his earlier 1963 libel case against the Hearst Corporation. This was due to the intervening landmark decision in New York Times Co. v. Sullivan, which established the "actual malice" standard for libel claims brought by public figures, necessitating that plaintiffs demonstrate not only the falsity of a statement but also deliberate fabrication.

Pauling's peace activism, extensive travels, and fervent foray into chemical-biomedical research collectively generated considerable opposition within Caltech. In 1958, the Caltech Board of Trustees mandated his resignation as chairman of the Chemistry and Chemical Engineering Division. Despite retaining his tenured position as a full professor, Pauling opted to depart from Caltech subsequent to receiving the Nobel Peace Prize funds. He then spent three years at the Center for the Study of Democratic Institutions (1963–1967). In 1967, he relocated to the University of California at San Diego, yet his tenure there was brief, concluding in 1969, partly due to political disagreements with the Reagan-era board of regents. From 1969 to 1974, he held a professorship in chemistry at Stanford University.

Vietnam War Activism

Throughout the 1960s, President Lyndon Johnson's escalating policy of American engagement in the Vietnam War catalyzed an anti-war movement, which the Paulings enthusiastically supported. Pauling publicly condemned the conflict as both superfluous and unconstitutional. He delivered speeches, endorsed protest letters, engaged in personal correspondence with North Vietnamese leader Ho Chi Minh, and submitted an extensive written response to President Johnson. However, his advocacy was disregarded by the American government.

In 1970, Pauling received the International Lenin Peace Prize from the USSR. He subsequently maintained his commitment to peace activism in the ensuing years. Together with his wife, Ava, he co-founded the International League of Humanists in 1974. Additionally, he served as president of the scientific advisory board for the World Union for Protection of Life and was a signatory of the Dubrovnik–Philadelphia statement issued between 1974 and 1976. Linus Carl Pauling held the positions of honorary president and member of the International Academy of Science, Munich, throughout his remaining years.

Furthermore, Pauling advocated for the Fair Play for Cuba Committee.

Global Activism

Pauling was among the signatories of an accord to establish a convention tasked with formulating a global constitution. Consequently, a World Constituent Assembly was convened, marking the inaugural instance in human history where such a body gathered to draft and ratify a Constitution for the Federation of Earth.

Eugenics

Pauling advocated for a restricted application of eugenics, proposing that individuals carrying defective genes should be subjected to mandatory visible marking, such as a forehead tattoo. This measure was intended to deter potential partners with similar genetic predispositions, thereby aiming to diminish the incidence of offspring born with conditions like sickle cell anemia.

Medical Research and Vitamin C Advocacy

At the age of 40, in 1941, Pauling received a diagnosis of Bright's disease, a form of renal illness. Adhering to the counsel of Thomas Addis, who notably engaged Ava Helen Pauling in roles such as "nutritionist, cook, and ultimately deputy 'doctor'," Pauling became convinced that he could manage his condition through Addis's then-unconventional regimen of a low-protein, salt-free diet supplemented with vitamins. Consequently, Pauling's initial and deeply personal encounter with the concept of therapeutic vitamin supplementation proved favorable.

In 1965, Pauling's engagement with Abram Hoffer's work, Niacin Therapy in Psychiatry, led him to hypothesize that vitamins could exert significant biochemical effects independent of their established roles in preventing deficiency diseases. Subsequently, in 1968, Pauling authored a concise article in Science titled "Orthomolecular psychiatry," thereby naming the prevalent yet contentious megavitamin therapy movement of the 1970s. In this publication, he posited 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." The term "orthomolecular" was coined by Pauling to describe the therapeutic approach involving the adjustment of concentrations of naturally occurring bodily substances for disease prevention and treatment. These concepts established the foundation for orthomolecular medicine, a field not widely adopted by mainstream medical practitioners and subjected to considerable criticism.

In 1973, Pauling, in collaboration with Arthur B. Robinson and an additional colleague, established the Institute of Orthomolecular Medicine in Menlo Park, California, which was subsequently rebranded as the Linus Pauling Institute of Science and Medicine. While leading research focused on vitamin C, Pauling simultaneously pursued his theoretical investigations in chemistry and physics throughout his life. During his final years, he developed a particular interest in the potential efficacy of vitamin C in preventing atherosclerosis and authored three case reports detailing the application of lysine and vitamin C for alleviating angina pectoris. Throughout the 1990s, Pauling proposed an extensive protocol for managing cardiac disease through the administration of lysine and vitamin C. In 1996, a dedicated website was launched to elaborate on Pauling's therapeutic approach, which it designated as Pauling Therapy. Advocates of Pauling Therapy contend that cardiovascular disease can be effectively treated and potentially remedied solely through the utilization of lysine and vitamin C, thereby obviating the need for pharmaceutical interventions or surgical procedures.

Pauling's work on vitamin C in his later years provoked considerable debate. The concept of high-dose vitamin C was initially introduced to Pauling by biochemist Irwin Stone in 1966. Convinced of its efficacy, Pauling subsequently adopted a daily regimen of 3 grams of vitamin C for cold prevention. Motivated by his perceived personal benefits, he delved into the clinical literature, culminating in the publication of Vitamin C and the Common Cold in 1970. In 1971, he initiated an extensive clinical collaboration with British cancer surgeon Ewan Cameron, focusing on the application of intravenous and oral vitamin C as a therapeutic intervention for terminally ill cancer patients. This collaboration yielded numerous technical publications and a widely accessible book, Cancer and Vitamin C, which detailed their findings. Pauling significantly popularized vitamin C among the general public and subsequently released two studies involving 100 purportedly terminal patients, asserting that vitamin C administration extended survival by up to fourfold compared to control groups.

A subsequent re-evaluation of these claims in 1982 revealed significant incomparability between the patient cohorts, noting that the vitamin C group exhibited less severe illness at study entry and was classified as "terminal" considerably earlier than the control group. Further clinical trials, conducted by the Mayo Clinic under the direction of oncologist Dr. Edward T. Creagan, similarly concluded that high-dose (10,000 mg) vitamin C offered no superior efficacy over placebo in cancer treatment, nor did it confer any discernible benefit. The consistent failure of these clinical trials to demonstrate therapeutic benefit led to the consensus that vitamin C was ineffective in cancer therapy, prompting the medical establishment to categorize Pauling's claims regarding cold prevention and cancer treatment as unsubstantiated. Pauling vehemently rejected these conclusions, characterizing the studies' findings and the management of the final study as "fraud and deliberate misrepresentation." He specifically criticized the methodology for employing oral rather than intravenous vitamin C, highlighting that his original study utilized intravenous administration for the initial ten days. Furthermore, Pauling critiqued the Mayo Clinic investigations, citing that control subjects received vitamin C during the trial and that the treatment duration was insufficient. He argued for lifelong, continuous high-dose vitamin C for cancer patients, contrasting this with the Mayo Clinic's second trial, where patients received vitamin C for a median period of 2.5 months.

Ultimately, the unfavorable outcomes reported by the Mayo Clinic studies largely curtailed widespread interest in vitamin C as a viable cancer treatment. Notwithstanding these findings, Pauling persisted in advocating for vitamin C in the management of cancer and the common cold, collaborating with The Institutes for the Achievement of Human Potential to explore its application in treating children with brain injuries. Subsequently, he partnered with Canadian physician Abram Hoffer to develop a micronutrient regimen, incorporating high-dose vitamin C, intended as an adjunctive cancer therapy. A 2009 review additionally highlighted methodological discrepancies among the studies, specifically noting the Mayo Clinic's omission of intravenous vitamin C, and recommended further investigation into the therapeutic potential of intravenously administered vitamin C. However, the preponderance of clinical trial data indicates that modest vitamin C supplementation, either alone or in combination with other nutrients, confers no demonstrable benefit in cancer prevention.

Personal Life

Linus Pauling married Ava Helen Miller on June 17, 1923. Their marriage endured until her passing in 1981. The couple had four children. Their offspring included Linus Carl Jr. (1925–2023), who pursued a career as a psychiatrist; Peter (1931–2003), a crystallographer at University College London; Edward Crellin (1937–1997), a biologist; and Linda Helen (born 1932), who married the distinguished Caltech geologist and glaciologist Barclay Kamb.

Pauling was raised within the Lutheran tradition but subsequently affiliated with the Unitarian Universalist Church. In a published dialogue with Buddhist philosopher Daisaku Ikeda, conducted two years prior to his demise, Pauling publicly affirmed his atheistic stance.

On January 30, 1960, while staying at a cabin approximately 80 miles (130 km) south of Monterey, California, Pauling embarked on a walk along a coastal trail. He became disoriented and attempted to ascend a rocky cliff, eventually reaching a substantial overhanging rock situated approximately 300 feet (90 m) above the ocean. Deeming it safest to remain in that location, he was subsequently reported missing. After enduring a night on the cliff, he was located nearly 24 hours later.

Death and Legacy

Linus Pauling passed away from prostate cancer on August 19, 1994, at his residence in Big Sur, California, at the age of 93. Although a grave marker was erected for him by his sister Pauline in Oswego Pioneer Cemetery in Lake Oswego, Oregon, his ashes, along with those of his wife, were not interred there until 2005.

Pauling's groundbreaking discoveries significantly advanced a wide range of scientific disciplines, evidenced by approximately 350 publications spanning quantum mechanics, inorganic chemistry, organic chemistry, protein structure, molecular biology, and medicine.

Pauling's seminal research on chemical bonding established him as a foundational figure in modern quantum chemistry. His influential treatise, The Nature of the Chemical Bond, served as a definitive reference for decades, introducing concepts such as hybridization and electronegativity that persist in contemporary chemistry curricula. Although his valence bond approach exhibited limitations in quantitatively explaining certain molecular properties, such as the coloration of organometallic complexes, and was subsequently superseded by Robert Mulliken's molecular orbital theory, modern valence bond theory continues to be a competitive framework alongside molecular orbital theory and density functional theory (DFT) for elucidating chemical phenomena. Furthermore, Pauling's contributions to crystal structure were instrumental in predicting and clarifying the architectures of intricate minerals and compounds. His identification of the alpha helix and beta sheet constitutes a cornerstone for the investigation of protein structure.

Francis Crick recognized Pauling as the "father of molecular biology." Pauling's identification of sickle cell anemia as a "molecular disease" pioneered the investigation of genetically inherited mutations at a molecular resolution.

In 1951, Pauling, in collaboration with Robert B. Corey and H. R. Branson, published "The Structure of Proteins: Two Hydrogen-Bonded Helical Configurations of the Polypeptide Chain," a pivotal early discovery within the nascent field of molecular biology. This publication received a Citation for Chemical Breakthrough Award from the Division of History of Chemistry of the American Chemical Society, which was presented to the chemistry department at Caltech in 2017.

Commemorations

During the late 2000s, Oregon State University finalized the construction of the $77 million, 100,000-square-foot (9,300 m2) Linus Pauling Science Center. This facility currently accommodates the majority of Oregon State's chemistry classrooms, laboratories, and instrumentation.

On March 6, 2008, the United States Postal Service issued a 41-cent commemorative stamp honoring Pauling, designed by artist Victor Stabin. The accompanying description highlights Pauling as: "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." This stamp sheet also featured other notable scientists, including biochemist Gerty Cori, astronomer Edwin Hubble, and physicist John Bardeen.

On May 28, 2008, California Governor Arnold Schwarzenegger and First Lady Maria Shriver declared Pauling's forthcoming induction into the California Hall of Fame, situated at The California Museum for History, Women and the Arts. The induction ceremony occurred on December 15, 2008, with Pauling's son, Linus Jr., accepting the accolade on his behalf.

Governor John Kitzhaber of Oregon officially designated February 28 as "Linus Pauling Day." The Linus Pauling Institute, which relocated from Palo Alto, California, to Corvallis, Oregon, in 1996, now operates as a component of the Linus Pauling Science Center at Oregon State University. The Ava Helen and Linus Pauling Papers, encompassing digitized copies of Pauling's forty-six research notebooks, are preserved within the Valley Library Special Collections at Oregon State University.

In 1986, Caltech honored Linus Pauling through a symposium and a lectureship. The Pauling Lecture series at Caltech commenced in 1989, featuring Pauling himself as the inaugural speaker. Subsequently, the Caltech Chemistry Department designated room 22 of Gates Hall as the Linus Pauling Lecture Hall, acknowledging his extensive presence within that space.

Other locations named in honor of Pauling include Pauling Street in Foothill Ranch, California; Linus Pauling Drive in Hercules, California; Linus and Ava Helen Pauling Hall at Soka University of America in Aliso Viejo, California; Linus Pauling Middle School in Corvallis, Oregon; and Pauling Field, a small airfield situated in Condon, Oregon, where Pauling spent his formative years. Additionally, a psychedelic rock band based in Houston, Texas, is known as The Linus Pauling Quartet.

Asteroid 4674 Pauling, located in the inner asteroid belt and discovered by Eleanor F. Helin, was named after Linus Pauling in 1991, commemorating his 90th birthday.

Linus Torvalds, the principal developer of the Linux kernel, and Linus Sebastian, a prominent YouTuber recognized for the technology-oriented channel Linus Tech Tips, both bear names attributed to Pauling.

Nobel laureate Peter Agre has publicly acknowledged Linus Pauling as a significant source of inspiration.

In 2010, the Pacific Northwest National Laboratory established its distinguished postdoctoral program, naming it the Linus Pauling Distinguished Postdoctoral Fellowship Program, in recognition of his contributions.

Honors and Awards

Pauling was conferred with numerous honorary degrees, approximately 47 by the time of his passing, commencing with an award from his alma mater in 1933. These distinctions included recognition from esteemed institutions such as Cambridge University, Oxford University, Princeton University, Reed College, and Yale University.

Awards and honors bestowed upon him throughout his career encompass the following:

Publications

Books