Pauling Couture

[Part of 2 of 4 in a series exploring Linus Pauling’s sense of style. Today’s post features photographs taken during the 1930s, 1940s and 1950s.]

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Baby Peter Pauling with his parents and brother Linus Jr. The family poses here in front of the Pauling home on Arden Road, Pasadena, 1931.

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The Paulings pose with an unidentified family. This photo marks an early appearance of Pauling’s beard. 1933.

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A relaxing moment with Linda, who is two years old in this photo. 1934.

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In lecture at Caltech, 1935.

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The beard returns, this time at Painted Canyon, California, a common getaway location for the Pauling family during the 1930s. Photo taken in 1935.

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A more formal portrait of Pauling with his beard, 1935.

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Dressed for cold weather at Niagara Falls. Of this moment, Ava Helen wrote: “It was so cold we wrapped scarfs around our heads and then put our hats on over the scarf.” The Paulings pose with their friend Yvonne Handy. Photo taken in 1938.

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Ava Helen and Linus photographed during a trip to Madison, Wisconsin, July 1939.

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Picnicking at Corona del Mar, California, 1940.

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In the laboratory with rabbits, 1942.

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Lecturing on structural chemistry at the Richards Medal ceremony. Pauling received this award from the Northeastern Section of the American Chemical Society in 1947.

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On holiday with the family of Carl Nieman, 1948.

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Posing with a new friend, 1948.

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And posing once more (and proudly) with the family car, 1948.

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In England with Lord and Lady Leverhulme, 1948. Pauling spent much of this year as a visiting professor at Oxford.

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In Hawaii, 1948.

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Another photo from the Hawaii trip, 1948.

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An early image of Pauling wearing what would become an iconic accessory for him – a black beret. Photo taken in 1953.

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Posing in front of the Fairpoint Street home, Pasadena, 1954.

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A publicity still of Pauling with a model of the alpha helix, 1954.

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In white tie and tux at the 1954 Nobel ceremonies.

 

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With Ava Helen at the old cabin, Deer Flat Ranch, 1957. Photo Credit: Arthur Dubinsky.

 

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Visiting Albert Schweitzer’s compound in Lambaréné, Gabon, 1959.

 

Clothes Make the Man

[Ed Note: The Pauling Blog becomes a photo blog for the next four weeks as we dig into the 5,500+ images held in the Ava Helen and Linus Pauling Papers. In addition to showing off some pictures that have never before been released online, this examination pays particular attention to Pauling’s evolving taste in clothes over the years. Today’s post features selections from Pauling’s birth in 1901 to the end of the 1920s.]

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Pauling in 1902, age 1. Note in particular the necklace.

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Pauling, age 5, posing in buffalo-skin chaps, 1906. Linus’s father had this photo commissioned for use in advertising his Condon, Oregon pharmacy.

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Linus, at center, with his two sisters, Lucile (left) and Pauline. This photo was also taken in Condon in 1908.

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Eight years later, the Pauling children posed near their home in Portland with their mother. From left to right: Lucile, Linus, Belle and Pauline Pauling, 1916.

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Pauling in his ROTC uniform during Fall term of his freshman year at Oregon Agricultural College. He is sixteen years old in this photo. Two years of ROTC was compulsory for all male students attending OAC at the time.

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An iconic portrait of the young Pauling taken the summer after his freshman year at OAC. Specifically, this photo was taken on the Oregon Coast in Tillamook, where the Paulings spent some time during the summer of 1918. Linus worked as a pin boy at a local bowling alley during the stay.

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Another photo of Pauling in his military dress, 1918. Though only two years were required, Pauling opted to remain in ROTC for the entirety of his OAC experience, graduating from the college having attained the rank of Major.

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Far from a typical look for Pauling, this image is cropped from a group photo of participants in the OAC “Feminine Section Intrafraternity Smoker,” circa 1920.

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Pauling with his life-long friend, Paul Emmett, in 1920. Also a Beaver, Emmett went on to become a major scientific figure in his own right, making significant contributions to the study of catalysis chemistry. Emmett also became Pauling’s brother-in-law when he married Pauline Pauling late in life.

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Pauling clowning around sometime near his graduation from OAC in 1922.

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Newly arrived at Caltech, Pauling poses on the back of a student’s car.

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Pauling with his bride, Ava Helen, her mother, Nora Gard Miller, and Nettie Spaulding, one of Ava Helen’s eleven siblings. Standing at front is Nettie’s daughter, Leone. 1924.

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The young couple outside their Pasadena home in 1925. Linus had been working on their Model-T Ford prior to this photo being taken.

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Looking very California on a trip to the beach. 1925.

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At the Temple of Neptune, Paestum, Italy, during his legendary Guggenheim trip to Europe. This photo was taken by Ava Helen in April 1926.

David Pressman

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David Pressman, 1937

[Part 6 of 6 in our series exploring Linus Pauling’s work on the serological properties of simple substances, and the colleagues who assisted him in this work.]

After a meeting with Karl Landsteiner in 1936, Linus Pauling began serious investigations into the link between antibodies and antigens, compiling notes for what would eventually become his serological series, a collection of fifteen papers published during the 1940s. Landsteiner had specifically piqued Pauling’s curiosity on the question of the human body’s specificity mechanism – e.g., how could the body produce antibodies tailored to lock onto and fight specific antigens?

Pauling ultimately surmised that the answer lie in the shape of the molecules, and in the type and number of bonding sites. He described this as a “lock and key” mechanism, otherwise termed as molecular complementarity. Throughout this project, which made a significant impact on the modern study of immunology, Pauling enlisted the help of many undergraduate, graduate, and doctoral students, including a promising young scholar named David Pressman.


David Pressman was born in Detroit, Michigan in 1916. He attended Caltech as an undergraduate, studying under Pauling and completing his degree in 1937. He stayed in Pasadena for his doctorate, earning it in 1940. During this time, he became a part of Pauling’s quest to unravel the structure of proteins, and was particularly involved with the antibody and antigen work.

By this point, Pauling and his colleague Dan Campbell felt confident enough in what they had learned about antibody specificity to attempt creating artificial antibodies. Pauling was enthusiastic about the practical application that such an endeavor might promise for physicians. Warren Weaver, Pauling’s primary contact at the Rockefeller Foundation, which was funding the work, cautioned Pauling against becoming overconfident, but still granted him enough money to hire Pressman full-time. Thus began Pressman’s career in immunology.

At Pauling’s request, Pressman stayed on at Caltech as a post-doc, and during this time the two became friends. In 1943, after failing to prove that they could synthesize antibodies, Pauling’s research team changed their focus from understanding the structural components of antibodies and antigens, to looking for the binding mechanism that allowed antibodies to attach to specific antigens through Van der Waals bonds. One outcome of this was their development of the theory of complementarity, a “lock and key” model in which molecules fit together because of the high levels of specificity that they show for one another.

Pressman authored three papers with Pauling during this phase, including a very important one titled “The Nature of the Forces between Antigen and Antibody and of the Precipitation Reaction,” published in Physiological Reviews. In this paper, the researchers discussed the historical significance of immunology within the context of structural chemistry. Speaking of the tradition in which they worked, Pauling and his colleagues wrote that “two of the most important advances in the attack on the problem of the nature of immunological reactions were the discovery that the specific precipitate contains both antigen and antibody, and the discovery that antibodies, which give antisera their characteristic properties, are proteins.”  In this paper, they also theorized that the immune system depends on structural and chemical forces to function.


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Pressman (at right) in the lab, ca. early 1960s.

In 1947, Pressman decided to pursue an interest in cancer research and moved on to the Sloan Kettering Institute in New York City to investigate the use of radioactive tracers as they pertained to cancer treatment.  The West Coast was never far from his thoughts however, and he often wrote back to friends comparing the two regions and asking for information about life in Pasadena. Of his new arrangements he observed, “The mechanics of living take a much greater part of the time in New York, so that I do not have as much time to do as much as I would like to or could do in Pasadena.”

Pressman’s first few years at Sloan-Kettering were difficult, not only because of the nature of the research that he was conducting – a continuation of the research that he started with Pauling – but because he was frequently forced to move both his lab and his residence, a source of continuous disruption for himself and his family. Sloan Kettering had just been established in the early 1940s and wasn’t formally dedicated until the year after Pressman moved there. Though it eventually became one of the nation’s leading biomedical research institutions, Pressman’s early experiences there coincided with institutional growing pains.

Eventually, as the environment at Sloan-Kettering became more stable, Pressman settled in to his position and provided Pauling with regular updates on his progress. The two often traded manuscripts back and forth, and each solicited technical advice from one another on their specific endeavors, which gradually grew further afield as time moved forward. At Kettering, Pressman continued to study antibody specificity and explored the potential use of radioactive antibodies for tumor localization to develop immunotoxins. In 1954, he left New York City for the Roswell Park Institution in Buffalo, remaining there until his death.


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60th birthday greetings sent to Pauling by David and Reinie Pressman, February 1961.

Pauling and Pressman remained in frequent contact for many years, focusing their voluminous correspondence primarily on work that Pressman continued to do as an outgrowth of their time together in Pasadena.  In July 1961, Pressman wrote that he and a colleague, Oliver Roholt, had potentially made a breakthrough with regard to the sequencing of the polypeptide chain associated with the region of specific binding sites in antibodies. He sent his manuscript, “Isolation of Peptides from an Antibody Site,” to Pauling for review prior to submission to Proceedings of the National Academy of Science. Pauling felt that the manuscript had been put together too quickly and challenged Pressman to do better. He annotated the manuscript with numerous suggestions, most of which Pressman adopted. Less than a week later, Pressman sent the manuscript back to Pauling with the corrections and Pauling transmitted it in to PNAS, where it was received favorably.

The late 1960s were a period of great activity and advancement for Pressman. In 1965, he received the Schoellkopf Medal, a prestigious award granted by the Western New York section of the American Chemical Society. In 1967, he became assistant director at Roswell and, in 1968, he published a book, The Structural Basis of Antibody Specificity. By all outside indications, Pressman’s life was going well.


In 1977 however, tragedy struck when Jeff Pressman, David and Reinie Pressman’s son, committed suicide at the age of 33. Jeff was an up-and-coming professor of political science at MIT, where he was well-liked by faculty and students. Up until a few months before his death, Jeff had seemed happy, both with his career and his life at home. In a letter to Pauling, Pressman described Jeff’s descent into depression as sudden, severe, and uncharacteristic. He also documented the events leading up to his son’s suicide, conveying that he and his wife had become increasingly convinced that the responsibility for the tragedy lay at the feet of a rheumatologist to whom Jeff had been seeking assistance for back pain.

Believing Jeff’s back pain to be primarily muscular in cause, the rheumatologist had prescribed Indocin in January 1977. According to multiple sources that Pressman later consulted, Indocin was a mood-changer, so much so that other patients had reported sudden depressive symptoms and, in severe cases, committed suicide a few months after starting the medication. To complicate matters, the rheumatologist had increased Jeff’s dose to a level that few patients could tolerate well, and had done so more rapidly than was advisable. When Jeff began complaining of insomnia, the rheumatologist prescribed two additional medications, both of which had the potential to worsen his depression. Jeff finally stopped taking Indocin, but the effects lingered. Jeff’s wife, Katherine, reported that Jeff had felt increasingly hopeless about his depression, even though he continued to work at MIT up until his death.


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David Pressman’s former secretary, Cheryl Zuber, posing with a plaque mounted in Pressman’s honor at the Cancer Cell Center, Roswell Memorial Institute, 1981.

In the wake of Jeff Pressman’s death, his colleagues at MIT published a collection of political essays dedicated in his honor. The dedication specifically called out Jeff’s commitment to his students and his impact as a teacher. In it, his colleagues wrote, “He cared deeply about public affairs and immersed himself in them because he genuinely felt that government at its best could improve peoples’ lives.”

Nonetheless, the loss took its toll and, for David Pressman, the only source of solace that he could identify was a return to work. In 1978, his focus in the laboratory was on localizing radio-iodinated antitumor antibodies. He later wrote to Pauling about chronic shoulder pain that he was experiencing, as he was aware of Pauling’s vitamin research and was in search of an alternative to the shoulder replacement surgery that had been recommended by his physician. Pauling put forth an argument for a megadose of vitamins, but Pressman was eventually diagnosed with osteoarthritis. By the end of the year, he was slowing down, both in his work and in his correspondence.

Two years later, in June 1980, Pauling received the news that David Pressman had jumped from the roof of Roswell Park Memorial Institute. In a letter to Pauling informing him of her husband’s death, Reinie Pressman cast about for answers. She wrote at length about the health problems that he had been experiencing, including partial hearing loss, prostate trouble, and chronic problems associated with the osteoarthritis in his right shoulder. She also confided that “You were a significant part of Dave’s happier past.” Pauling replied in kind, stating

I was very fond of David. Also, I owe much to him, because of the vigor and effectiveness with which he tackled scientific problems during the eight years that he worked with me. Much of the success of our program in immunochemistry was due to his contribution.

Carol Ikeda and Miyoshi Ikawa

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Linus Pauling, 1942

[Ed Note: Parts 5 and 6 of our series detailing Linus Pauling’s work on the serological properties of simple substances both focus on the intriguing life stories of three individuals with whom Pauling worked on this program of research.]

Over the years, Linus Pauling forged close relationships with many of his graduate and doctoral students, offering guidance that, in numerous cases, changed the course of a student’s career. During World War II, he fought particularly hard for two of his research assistants, Miyoshi Ikawa and Carol Ikeda. In both cases, Pauling’s intervention prevented these colleagues from being forcibly interned. Instead, Ikawa and Ikeda each moved on to graduate studies and fruitful careers in science.


Miyoshi “Mike” Ikawa was born in California in 1919 to first generation immigrant parents. He pursued undergraduate studies at Caltech, where he was a member of the Chemistry Club and Tau Beta Pi, and competed on the Fleming House wrestling team. When he graduated in 1941, he was already working in Pauling’s lab, preparing compounds and helping with the first three serological papers. Pauling subsequently served as his graduate advisor.

Carol Ikeda came to Caltech from Texas in 1939, having started his education at Paris Junior College in Texas. He transferred to Caltech with the intent to study chemistry and become an organic chemist. At Caltech, he stood out among many other very bright students; Pauling described him as “one of the top men in the class.” Not one to give compliments lightly, Pauling recognized Ikeda’s potential not only from his performance in class, but also from his work in organic research labs on campus. Before Ikeda had even decided to continue onto graduate studies at Caltech, Pauling had recruited him for the serological project as an assistant in the Immunochemistry department. Indeed, it is especially noteworthy that Ikeda and Ikawa both are listed as co-authors for Pauling’s first three serological papers, given that the first two papers were published while Ikeda and Ikawa were still undergraduates.


Up until World War II, it appeared that Ikawa and Ikeda were each moving well down the path toward successful careers in immunology, organic chemistry, or biochemistry. This all changed when President Franklin Roosevelt issued Executive Order 9066 and declared Pasadena to be a military zone.

Even before the attack on Pearl Harbor, U.S. citizens of Japanese descent faced discrimination on the basis of race as well as suspicions that they would prove more loyal to Japan than to the United States even if they were second- or third-generation citizens. Acutely aware of the mounting tension faced by American-born Japanese, Pauling was determined to support students bearing this burden and to make sure that they could find positions at Caltech for which they were suitably qualified.

Pauling was likewise clear in his understanding that other universities did not share his point of view. In the recommendations that he wrote, he provided full disclosure and acknowledged potential discomforts regarding race, an issue that many administrators would have preferred be left unacknowledged. In one particular reply to a request for recommendations, Pauling wrote

…the two best men scholastically in our graduating class are American born Japanese, Ikawa, and Ikeda. Although one of them has, I think, a satisfactory personality for teaching work, I doubt that you would be interested in appointing him because of his racial handicap.

Some universities responded positively to recommendations of this sort; the University of Iowa, for one, confirmed that race wouldn’t be a problem at all. Rather, Pauling’s Iowa contact assured that the institution shared Pauling’s stance and was committed to considering the qualifications of their applicants regardless of race. The reply went on to state,

While we have not had any American-born Japanese on our teaching staff, I see no reason why they would not get along satisfactorily, if they have the necessary intelligence and ability.


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Miyoshi Ikawa, 1941

Ikawa and Ikeda had been working on the serological project for more than a year when Pasadena was declared a military zone. Cognizant of the need to help his assistants relocate to a safer area, Pauling had a relatively easy time finding Ikawa a position as a graduate student at the University of Wisconsin, where he worked under Karl Paul Link. This move ultimately changed the course of Ikawa’s career. Before receiving his doctorate, Ikawa, along with Link and Mark A. Stahmann, synthesized warfarin and obtained a patent for it to be used as a rat poison. By 1950, warfarin (now commonly referred to as Coumadin) was being used to treat blood-clotting disorders such as thrombosis, because it was a strong anticoagulant. It still serves this purpose today.

With the war over, Ikawa was free to return to the West Coast, where he conducted postdoctoral research at Caltech and UC-Berkeley, before moving on to the University of Texas. In the early 1960s, he settled down and became a professor at the University of New Hampshire, where he began focusing on marine biotoxins. In 1972, he and his colleagues established the Paralytic Shellfish Monitoring Program for the state of Maine, a course of action that followed the first evidence of a red tide in the southern Gulf of Maine. Ikawa taught at the University of New Hampshire for twenty years and then spent most of his later career advising technical panels and partaking in peer review committees for federal research grants. He passed away in 2006.


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Carol Ikeda, 1941

Pauling had a harder time finding a position for Ikeda. In February 1942, shortly after Roosevelt released his executive order, Pauling sent a letter to Robert Millikan – the chairman of the Caltech Executive Council – about Ikeda’s progress and position. In this, Pauling tried to make the case that, while his serological research wasn’t directly related to defense work, its results could be valuable for their medical application. He also pointed out that finding someone as competent as Ikeda to continue these studies would be nearly impossible.

As it turned out, this approach backfired for Pauling, because so many people were nervous about having American-born Japanese involved in any war effort. Consequently, Millikan asked Pauling to vouch for Ikeda’s loyalty in order to allow Ikeda to continue “to undertake, under special arrangement, research work which may involve defense matters.” Pauling vouched for Ikeda’s work, but hesitated to comment on his loyalty, because he felt that someone with a more personal working relationship with Ikeda could give a better answer. He also suggested that Ikeda could be transferred to a teaching position if the issue of loyalty could not be resolved to Millikan’s satisfaction.

As Millikan deliberated, Pauling began to feel that Caltech might not be the best environment for Ikeda, even if he was transferred to a teaching position. In short order, Pauling contacted Michael Heidelberger, a faculty member at Columbia University’s College of Physicians and Surgeons. In doing so, Pauling offered Heidelberger a quid pro quo of sorts, suggesting that Heidelberger accept Ikeda into his program at Columbia in exchange for Pauling hosting one of Heidelberger’s researchers in Pasadena. This plan broke down when the Columbia researcher that Pauling had in mind wrote back to say that he could not accept an appointment at Caltech and that he wished to stay on at Columbia instead.

The situation was not improved much by Heidelberger’s blasé attitude toward the internment camps. Recognizing that “wholly” patriotic people would be unjustly punished, Heidelberger remained unconvinced that there was much that he or Pauling could do to alleviate the issue, an opinion shared by many. As would later become the norm, Pauling stood out here as a lonely voice in the scientific community.

For Ikeda, things worked out at the last minute. In April 1942, just two weeks before Ikeda was assigned to report to a camp, Pauling managed to find him a graduate position at the University of Nebraska, where he completed his Ph.D. in 1945. In 1947, Ikeda accepted an offer of employment from DuPont in Delaware, and then later moved within the company to Philadelphia. In 1962, he received a patent for a resinous coating material that he developed while working for DuPont. He passed away in Phoenix, Arizona in 1996, having enjoyed a successful life and career.

A Master of Many Fields

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Linus and Ava Helen Pauling, Oxford, 1948.

[The serological properties of simple substances – part 4 of 6]

By the Spring of 1946, having published no fewer than twelve articles – over a little more than three years – on the serological properties of simple substances, Linus Pauling’s busy life began to get in the way of continued advancement of his research program. Perhaps chief among competing interests was a separate fifteen-year joint research program, funded by a $300,000 grant, that Pauling and George W. Beadle, the head of Biology at Caltech, were in the midst of setting up.

Pauling had also returned to studies of sickle cell anemia with the arrival of Dr. Harvey Itano in the fall of 1946. He was likewise engaged with new inquiries in inorganic chemistry that reached a crescendo with a famous article, “Atomic Radii and Interatomic Distances in Metals,” published in March 1947. From there, the dawn of 1948 saw Pauling moving to England, where he served as George Eastman Professor at Oxford University. Not long after, he received the Presidential Award for Merit for work done during World War II. Clearly there was much going on in Pauling’s world.


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Drawings of antibodies and antigens made by Linus Pauling in the 1940s.

Nonetheless, consequential progress continued to be made in the serological program with the thirteenth paper – an important one – coming into print in April 1948, while Pauling was still in England. This article, written by Pauling along with David Pressman and John Bryden, marked a continuation of the precipitation experiments that had been carried out in the previous two papers, but this time with a different antiserum and antigen substitute. The Paper XIII experiments determined that antibodies are rigid and cannot change shape to bond to a different antigen.

Significantly, these data also confirmed that structural complementarity was responsible for the reaction’s specificity, affirming Pauling’s early notions of a “hand in glove” fit. Furthermore, the paper’s findings established that the principal forces involved in the complementary bonds were Van der Waals interactions – very weak bonds induced by sheer proximity. In short, the experiments verified the importance of intermolecular interaction in the specificity of serological reactions, a significant breakthrough.


With Pauling now having returned stateside, the year 1949 saw the publication of the final two serological articles, one released in January and another during the summer. Paper XIV, written by Pauling and Arthur Pardee, was fashioned as a response of sorts to disagreements that had been expressed by other scientists concerning Pauling’s interpretations of his experimental results.

The paper specifically focused on experiments utilizing simple antigens and purified antibodies, rather than the antisera that Pauling had been using. These trials found that, although the behavior of simple antigens was different when matched with purified antibodies rather than antisera, “…the earlier work, carried out with serum, is presumably reliable.” In making this statement, Pauling and Pardee cited the non-specific combination of dye molecules along with other components of the serum for past results that had varied slightly.

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Illustration of the antibody-antigen framework, 1948.

The last article in the serological properties series, Paper XV, appeared in the Journal of the American Chemical Society in August 1949; Pauling and Pressman were its authors. The article detailed the results of experiments using an antiserum with two or more positive charges. This experimental set-up, Pauling hoped, would allow him to determine the difference in combining power between antibodies containing only one negative charge as well as those containing two negative charges. The duo discovered that the antibody would only combine strongly with antigens that contained two negatively charged groups in specific positions. From this, Pauling concluded that the attraction between the negative charges of the antigen and the positive charges of the antibody are very strong.

After completing the fifteenth paper, Pauling largely left immunology behind in favor of the work that he and Itano were doing on sickle cell anemia. In 1950 and 1951, Pauling and several collaborators also published multiple articles delineating protein structures. In addition, it was during this time that Pauling began to really ramp up his peace work, delivering more and more lectures on the topic as the years went by.


The fifteen articles that comprise Pauling’s serological properties series were published over a span of seven years. During that period, Pauling worked with twelve collaborators, several of whom were graduate students. By the conclusion the project, hundreds of experiments, using dozens of compounds, had been run.

Particularly given the fact that he lacked any sort of formal background in immunology, the massive impact that Pauling made on the field is truly impressive. By the time that he moved on to other topics, Pauling’s work had served to raise the level of immunological knowledge by orders of magnitude. He is credited now with having discerned a relatively complete understanding of both antibody structure as well as the reaction mechanics underlying the interplay between antigens and antibodies. He also applied the vast collection of data that he had compiled to develop a theory of antibody formation. Of this, biographer Tom Hager wrote

For fifteen years…until a new, more powerful theory of antibody formation was put forward, Pauling’s idea led the field. His antibody work again expanded his growing reputation as a master of many fields.

Pauling himself believed that this work had solved “the general problem of the nature of specific biological forces” and that this understanding would “permit a more effective attack on the many problems of biology and medicine.”

Indeed, Pauling’s work with antibodies was influential even outside of the field of immunology. In 1990, journalist Nancy Touchette declared, “In his 1946 paper [“Molecular Architecture and Biological Reactions”], Pauling prophesied about the future of biology and medicine and why understanding the nature of complementarity is so important to the future of the field.” Five years later, at a Pauling symposium held at Oregon State University just a few months after Pauling’s death, molecular biologist Francis Crick stated flatly that Pauling “was one of the founders of molecular biology.” Once again, Linus Pauling had revolutionized a scientific field while following his curiosity and intuition.

A Period of Rapid Advancement in Pauling’s Immunological Work

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Dan Campbell and Linus Pauling in a Caltech laboratory, 1943.

[Part 3 of 6 in a series investigating Pauling’s work on the serological properties of simple substances.]

In April 1943, only four months after releasing his first four papers on the serological properties of simple substances, Linus Pauling was ready to publish more. His fifth paper in the series reported out on the results of hapten inhibition experiments that his lab had conducted using two different antibodies. In the experiments, “measurements were made of the inhibitory effect of each of twenty-six haptens on one antigen-antibody reaction, and interpreted to give values of the bond-strength constant of the haptens with the antibody.”

The results of the experiments, with particular attention paid to the twenty-six hapten molecules, were then discussed in the context of their possible molecular structure. In this discussion, Pauling pointed out that some of the polyhaptenic molecules did not produce participates, a detail that was explained as having been caused by steric hindrance, or the inability for a reaction to take place due to molecular structure.

David Pressman was again a co-author of the paper, as were two graduate students, John T. Maynard and Allan L. Grossberg. Grossberg would stay with Pauling’s lab until 1946 – two years after completing his war-time master’s degree – and was involved with three more papers from the series. He later went on to work with Pressman at the Roswell Park Memorial Institute and eventually became associate chief of cancer research there.


Pauling’s immunological work was quickly producing exciting new results, momentum that was recognized by The Rockefeller Foundation, which awarded Pauling another grant in June 1943. Pauling also began delivering lectures on his serological research, notably including the Julius Stieglitz Memorial Lecture in January 1944.

Articles six, seven, and eight of the serological series were each published a few months apart from one another, beginning in March 1944. Pauling co-authored these papers with previous collaborators Pressman, Campbell and Grossberg, and also with Stanley Swingle, a research fellow and instructor who had earned his Ph.D. at Caltech in 1942.

Paper VI put forth more evidence for the Marrack-Heidelberger framework theory, for which Pauling had first announced his support in Paper I. The experiments specified in Paper VI made use of fifty different substances possessing either one, two, or three haptenic groups. The results of these trials indicated that a substance containing two different haptenic groups would only form a precipitate when antisera binding to both of those two groups were present. Of this finding the article states, “this provides proof of the effective bivalence of the dihaptenic precipitating antigen, and thus furnishes further evidence for the framework theory of antigen-antibody precipitation.”

In the seventh paper, published in May 1944, Pauling returned to the simple theory for calculating the inhibition of precipitation that he had developed in Paper II, published at the end of 1942. In his discussion, Pauling reported that his laboratory’s experiments found general qualitative agreement with the theory, but the numbers tended to be off. In seeking a more reliable equation, Pauling worked to improve the theory, accounting now for the fact that a single antiserum can contain slightly different antibody molecules with assorted combining powers.

This new and improved theory, and the equation that accompanied it, agreed with experimental results much better than had the original proposal. Indeed, by accounting for variations in the antibodies, Pauling and his colleagues had succeeded in developing a “quantitative theory of the inhibition by haptens,” which would prove important to much of the work that was to come.

Paper VIII, “The Reactions of Antiserum Homologous to the p-Azobenzoic Acid Group,” appeared in October 1944 and shared the results of experiments done with a new type of antibody. Previously, experiments had been conducted with antisera homologous to two different acid groups. However, in these new investigations, the Caltech researchers used antisera homologous to another type of acid group. In doing so, Pauling and his colleagues were attempting to gauge optimum acidity levels for serological reactions; to identify the types of antigens that most readily cause precipitation; to likewise identify haptens that inhibit precipitation; and to measure the strength of their inhibiting power.

Despite Pauling’s extensive involvement in studying reactions of antibodies and antigens, he still had time for other research interests. In February 1945, Pauling and Campbell announced that they had created a usable substitute for blood plasma, the result of three years of work supported by military contracts. Shortly thereafter, Pauling learned a few key details about sickle cell anemia while meeting with the other members of the Medical Advisory Committee. He immediately thought that hemoglobin was involved and went on to experimentally prove that the disease located its source on the molecular level; a first in the history of science.


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Arthur Pardee, 1980

June, July, and September of 1945 each saw the publication of another serological article: Papers IX, X, and XI respectively. The final two of this set featured the addition of a pair of new collaborators. John Bryden, a co-author for Paper X, completed his master’s degree around the time that the article was published, and Arthur Pardee was in the middle of his doctoral program when he worked on Paper XI. Pardee also worked on the experiments described in Paper XIV, although the article was published after he had completed his Ph.D. and returned to Berkeley. Pardee later went on to enjoy a hugely successful career as the Chief of the Division of Cell Growth and Regulation of the Dana Farber Cancer Institute at Harvard Medical School.


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Karl Landsteiner

Papers IX and X shared the results of still more inhibition experiments. The experiments reported on in Paper IX largely confirmed Karl Landsteiner’s discovery on the combining of antiserum and antigen, or antiserum and hapten. Landsteiner had found that less bonding occurred between antibody and antigen or antibody and hapten if the substituent groups on the binding molecule were different from the antigen that created the antibody. The Pauling group confirmed this theory and, in addition, described the forces that affect hapten inhibition. Pauling believed that it had to do with intermolecular forces “including electronic van der Waals attraction…the formation of hydrogen bonds, and steric hindrance,” a supposition that would play a crucial role in later papers in which Pauling explained the incredible specificity that governs the behavior of these molecules.

Paper X studied the effect of molecular asymmetry on serological reactions. In this series of experiments, Pauling and two collaborators, David Pressman and John Bryden, had prepared an antiserum with an optically inactive immunizing antigen; e.g., a molecule that does not rotate plane polarized light. However, even though the immunizing antigen was not optically active, the antibodies in the serum combined more strongly with one configuration over an optically active hapten, which does rotate light, than in the other configuration. Pauling and his colleagues hypothesized that this was due to the presence of optically active amino acid residues in the antibody molecules.

Paper XI, published in September 1945, discussed reactions of antisera with various antigen substitutes. In this instance, the Pasadena group measured the precipitate formed by these reactions to gauge the inhibiting power of the haptens. They then correlated hapten-inhibiting power to molecular structure, suggesting that if a substance mixed with antisera more readily, then the structure of the molecule might be smaller. They ultimately discovered that if a hapten structure matched an immunizing azoprotein structure, the haptenic group exhibited a strong inhibitory effect.

In February 1946, Pauling and co-authors Pressman, Grossberg, and Leland Pence published the twelfth serological article. This was Grossberg’s fourth and final contribution; ultimately, he served as co-author on more of the series than did any other collaborator, save David Pressman and Dan Campbell. New to the series was Leland Pence, an assistant professor of organic chemistry at Reed College who had been collaborating with Pauling since 1942.

Prior to Paper XII, all previous experiments carried out by the lab had used negatively charged or neutral compounds. Paper XII presented the results of experiments that used a positively charged antibody. Pauling and his collaborators found that, even when using positively charged antibodies, hapten inhibition occurred the same way, with the same factors, as was the case with a negative or neutral compound. That said, one important difference that was observed was the ideal acidity for maximizing precipitates; when using a positively charged antibody, the pH required for the optimum amount of precipitate was much lower.

Analyzing Precipitation Reactions Between Simple Substances

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Linus Pauling, 1942

[Part 2 of 6 in a series investigating Pauling’s work on the serological properties of simple substances.]

The first four papers published by Linus Pauling and his Caltech colleagues on the serological properties of simple substances described general aspects of the precipitation reactions that occur between antibodies and antigens. This work was spurred by a fundamental conundrum: Pauling and many others knew that antibodies and antigens would react to form solid precipitates. However, because the chemical structures of these precipitates were, at the time, so difficult to determine, scientists had been unable to decipher crucial details about the antibodies and the antigens that combined to form them.

Pauling’s solution to this problem was to investigate the products of a reaction that utilized, in part, a chemical compound whose structure he already knew. The constituents of these products were a simple organic compound consisting of carbon, oxygen, and hydrogen, combined with one or more haptenic groups – small molecules that spur the formation of antibodies when coupled with a larger molecule. Employing this methodology would, Pauling felt, allow him to better approximate the make-up of the antibody, because the experiment now involved only one unknown structure.


In order to run the experiments, Pauling set up a standard protocol for preparing the compounds that he needed. Each experiment required three types of compounds: simple antigens used in the precipitation reactions; immunizing antigens used to create antibodies; and antisera, which are liquids containing antibodies formed through the coagulation of blood. Pauling used this method for all of his serological reaction experiments.

Pauling and his collaborators obtained the antisera by injecting rabbits (some of them housed in Pauling’s yard and cared for by his children) with immunizing antigens. The rabbits then produced antibodies to combine with and neutralize the immunizing antigens. Once the last injection was carried out, the scientists drew blood from the rabbits, allowed it to clot, and collected the antiserum.

The reactants for Pauling’s experiments – immunizing antigens and simple antigens – were either purchased or prepared by Pauling and his collaborators, typically the graduate students.

For each precipitation test, equal portions of antiserum and a saline solution containing a simple antigen were mixed together. Typically, four to six different concentrations of antigen were used. The mixtures stood at room temperature for one hour, then were refrigerated overnight. The next day, a centrifuge was used to separate out the precipitates, which were then washed with saline solution and analyzed. Pauling’s method of analysis involved measurements of nitrogen, arsenic, carbon, and hydrogen. From there, the amount of a given antibody in the precipitate was determined using the nitrogen measurements.

The initial set of experiments used twenty-seven different compounds as the antigen, each containing between one and four haptenic groups. All of the polyhaptenic substances – those that had more than one haptenic group per molecule – formed precipitates, but none of the monohaptenic substances did. This finding supported the framework theory, devised by the British chemist John Marrack in 1934, that postulated that multivalent antibody molecules could combine with polyhaptenic molecules to form large aggregates, which would become precipitates. On the other hand, Marrack suggested, if multivalent antibody molecules combined with monohaptenic molecules, only small complexes would form and these would not precipitate.

Pauling summarized this work in a set of four papers that were published in the December 1942 issue of the Journal of the American Chemical Society.


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John Richardson Marrack

Pauling’s first article, “Precipitation Reactions between Antibodies and Substances Containing Two or More Haptenic Groups,” served primarily to provide support for Marrack’s framework theory. Eight years before, Marrack had stated that antibodies were multivalent; in other words, they can bond to more than one antigen molecule. In order for them to bind in this way, the molecules must be properly oriented such that the binding sites fit together. This causes the formation of a lattice-like structure which grows until it is too large to stay in solution and precipitates out.

As noted above, Pauling’s experiments found that “simple antigens containing two or more haptenic groups per molecule were found to give precipitates with the antisera, whereas the seven monohaptenic substances failed to precipitate,” a discovery that confirmed the validity of the Marrack-Heidelberger framework, or lattice theory.

The second paper in this installment was titled “The effects of changed conditions and of added haptens on precipitation reactions of polyhaptenic simple substances.” The alterations to conditions that were tested by Pauling included allowing the mixture to rest longer, changing its temperature, and altering its pH. Having confirmed his own belief, in Paper I, that antibodies are multivalent, Pauling used Paper II to first note his assumption – and provide evidence for – bivalence.

In addition, Pauling used this paper to publish an equation that could be employed to find the amount of a precipitated compound in a given solution based on solubility, equilibrium constant, and total amount of hapten. Notably, the equation led Pauling to deduce “that in each case the maximum amount of precipitate is produced by an amount of antigen approximately equal to the amount of antibody,” an idea that unfolded more fully in the following paper.

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The equation published by Pauling in Paper II.

Paper III, “The composition of precipitates of antibodies and polyhaptenic simple substances; the valence of antibodies,” further explores the supposition of bivalence through an examination of the ratio of antibody to antigen in precipitates.

While the bulk of Pauling’s experiments focused on dihaptenic antigens, some used trihaptenic antigens, and others used tetrahaptenic antigens. Through careful analyses of the different precipitates that resulted, Pauling was able to determine that the ratio of antibody to antigen in any given precipitate was approximately 1:1.

This finding suggested that most antigens could have only two antibody molecules attach to them, even if they possessed more than two haptenic groups, since the antibody molecules were relatively large and interfered with one another’s attachment. Pauling also used the one-to-one ratio to conclude that most antibody molecules possess two binding sites. The major development of this paper – the near one-to-one ratio – was “taken to indicate bivalence of most of the antibody molecules.”

The last paper of the first installment, Paper IV, reported the results of initial experiments on the inhibition of precipitation in the presence of hapten. Pauling and his colleagues had tested precipitate inhibition in three basic ways: by altering temperature, by augmenting the amounts of hapten present in their mixtures, and by isolating the effects of twenty-four specific haptens. These experiments found that adding haptens to a mixture of antibodies and antigens inhibited the precipitation of the antibody-antigen complex.

Furthermore, Pauling concluded that the structure of the haptens correlated with their inhibition power and detailed the relative values of each hapten’s bond strength. He then used the hapten inhibition data from these experiments to update his earlier equation for finding the amount of antibody precipitated.

Next week, we’ll examine eight more papers that Pauling published on the topic over the next three years and explore the ways in which this body of research evolved and expanded during that time.