[Introductory remarks by Crellin Pauling]

Matt Meselson: Much has been written about Linus Pauling as a great scientist. I will speak today about Linus Pauling as an educator and as an example to young scientists. Biographers may not have given adequate attention to this major dimension of Pauling's life and to how it relates to his other activities.

Pauling was immensely involved with teaching chemistry. My impressions are based on having been a freshman at Caltech in 1950-51 and on seven years as a graduate student, research fellow, assistant professor, and seminar research fellow, all in the division of chemistry and chemical engineering. As a freshman I took Pauling's course in introductory chemistry and also was an undergraduate researcher for him. I left Caltech and did some other things and then I came back and became a graduate student with Linus in 1953. In the 1950s, Linus taught three extremely popular courses: General Chemistry, Quantum Mechanics, and The Nature of the Chemical Bond. Each was based on a separate textbook that Pauling had authored: General Chemistry, first published in 1947 with two subsequent editions in 1953 and 1970; Introduction to Quantum Mechanics, written with his former student E. Bright Wilson, published in 1935 and reprinted in 1985; and The Nature of the Chemical Bond in three editions, 1939, 1940, and 1960.

In addition to classroom undergraduate teaching, Pauling directly supervised individual undergraduate research students. He also gave numerous talks and wrote articles about chemical education and careers in chemistry. He introduced innovations in pedagogy at Caltech. One of these, of which he was very fond, was the proposition system: graduate students working for their doctoral degrees were required to submit, and defend at their oral doctoral examination, ten propositions. This assured, according to Caltech regulations at the time, "originality, breadth of interest, and soundness of training." From the start of one's graduate work you were always collecting, like a hand in poker, a set of propositions, and then you would think of a better idea and throw out one that was not as good. There was a lot of emphasis placed on these, not only because it was a requirement, but because often the faculty was bored with the thesis itself and looked forward to attacking the student. And the student looked forward to attacking back. We were allowed to have a "secret" proposition, too: one which was given to the faculty examiners only at the time of the exam, so they could not study up on it. In fact, Martin Karplus, who was a graduate student of Pauling's when I was, submitted his secret proposition in code. I do not think his committee ever cracked it, so they could not challenge him about it. He could sit there and smile, and say "I'm certain this is correct" and they had no way to attack it. He is at Harvard now and I have asked him every year if he would finally tell me what this proposition was, and to this day, he will not.

Anyway, this was a very effective system for making us think broadly; some of the propositions had to be outside your field. Of course, Pauling supervised a large number of graduate students. I was his last graduate student at Caltech. There were six at that time: Bill Sly, who is now a professor of chemistry at Harvey Mudd College in Claremont, California; Joe Kraut, who is a professor at UCSD, in La Jolla; Martin Karplus, who is a professor of chemistry at Harvard; Elihu Goldish, who is a professor of geology at Cal State at Long Beach; Gary Felsenfeld, who is Section Chief of Physical Chemistry in the molecular biology part of the National Institutes of Health, and me. Goldish, Felsenfeld, and Karplus shared a house on Coleman Street and I lived there with them for a short time. I do not know if the biographers of Linus have spoken with any but a very few of his many graduate students.

Starting in 1937, Pauling was chairman of the Caltech Division of Chemistry and Chemical Engineering. I wonder if biographers have spoken with contemporary members of the Caltech Division of Chemistry and Chemical Engineering about Linus' influence and activities regarding the curriculum, or the setting of degree requirements, or his views on education, or to what extent he seemed to emphasize education in faculty meetings. After all, Pauling wrote many articles and gave many lectures explaining chemistry to the general public.

Another question biographers might consider is "what is the relationship between Linus as an educator and as a political activist?" It was said this morning that he was unsophisticated in political matters. But this view itself may lack sophistication. After all, Linus set a nuclear test ban as his objective and he got results. Considering the fact that Pauling devoted so large a part of his life to education, the educator in him must have had an important influence both on his scientific research and on his political activity.

But rather than addressing these questions further, I am now going to tell you some stories. Linus taught with great enthusiasm. He often asked his class challenging questions, and he encouraged the class to ask questions back. His manner of teaching was very interactive, more interactive even than that of Dick Feynman, who had a very interactive way of teaching. Linus spiced it up with entertainment. He gave out candy for right answers. (I remember asking him to leave out chocolate, because I am allergic to it.) He had a marvelous slide rule, from which he could get answers to many significant figures. It was only a little slide rule. That may not have been illusory: it is possible to develop a long answer in the form of the expansion of a series. I do not know if he was doing that or if he had just memorized the answers.

One trick he liked to play was to put a very small piece of sodium in a beaker of water. Of course that generates a nice explosion. And then he would have another beaker, full of kerosene -- and, dropping in a much larger piece of sodium, he would say, "Now you are going to see something really interesting!" Of course, sodium does not react at all in kerosine and that is more interesting than just a bigger explosion.

In my freshman year Linus asked me to conduct some research, and I remember that the way he talked to me surprised me. He talked to me as though I were another scientific colleague, even though I was just a miserable little undergraduate. I think that was his usual manner with his students, to talk with students as though they were scientific colleagues. It was very challenging, but also could make you feel great. The problem he gave me was to synthesize a series of alkyl isocyanides and to measure their binding with the hemoglobin of a marine worm named Eurechis. You find these worms at the Caltech marine lab at Corona del Mar, in the sand. If you find one, and dig it out, and squeeze it, it squirts water for maybe five feet, and you can squirt your friends with it. The idea was to test Pauling's 1949 view, (also put forward independently by Jeffries Wyman), that the oxygen equilibrium curve of hemoglobin is sigmoid in shape not because of direct interactions between the hemes, but rather because of steric effects of oxygen binding on the conformation of the protein, making the hemes more accessible each time another oxygen is added. At the end of that academic year, I went to him to confess that I had managed to synthesize a series of alkyl isocyanides, but I had not done a single binding experiment to Eurechis hemoglobin. I expected him to voice stern disappointment, but instead he cheerfully said that in fact I had learned what he intended. I had learned a valuable lesson, he said, namely that beginners often greatly underestimate how long it will take to do a piece of research. I do not know if that is what he really thought, but he was certainly nice about it.

Two years later I came back to Caltech as a graduate student. I took his course, The Nature of the Chemical Bond. There were a lot of problem sets for students to solve. I remember the excitement of learning from one of those problem sets how you could estimate the ratio of the strength of the hydrogen bond to that of the deuterium bond simply from the quantum-mechanical zero-point energy. That got me interested in stable isotopes, and that got me interested in things that, later, Frank Stahl and I did at Caltech in biology.

I became a graduate student of Pauling's by an accident that involved a swimming pool. One afternoon in the summer of 1953 Peter Pauling, Linus' middle son, had some friends over for a swim. Linus came out of the house, dressed in a tie and a jacket, and peered down at me (I was in the water, not at all well-dressed) and he said "Well, Matt, what are you going to do next year?" (You've got to have this picture in your mind-I am all wet, largely naked, looking up at the world's greatest chemist, who is wearing a tie and a jacket. For someone growing up in California, that alone is intimidating). So I said I was going to go back to the University of Chicago, where I had been before, and I was going to be a graduate student of the Committee on Mathematical Biophysics. It was the only time I ever saw Linus looking amazed. After a moment he said, "But Matt, that is a lot of ... baloney! Why don't you come to Caltech and be my graduate student?" So I looked up at him and said, "Okay, I will." And that was that.

That fall, in 1953, it came time for me to have a research problem, so I went to see Linus in his office in the Crellin Lab, and he took a rock down off of a shelf near his desk and announced that this was a tellurium mineral -- he had worked on tellurium minerals, years earlier -- and that this would have an interesting crystal structure. The discussion went something like this:

LP: Well, Matt, you know about tellurium, the group VI element below selenium in the periodic chart of the elements?
Me: Uh, yes. Sulfur, selenium, tellurium ...
LP: I know that you know how bad hydrogen sulfide smells. Have you ever smelled hydrogen selenide?
Me: No, I never have.
LP: Well, it smells much worse than hydrogen sulfide.
Me: I see.
LP: Now, Matt, Hydrogen telluride smells as much worse than hydrogen selenide as hydrogen selenide does compared to hydrogen sulfide.
Me: Ahh ...
LP: In fact, Matt, some chemists were not careful when working with tellurium compounds, and they acquired a condition known as "tellurium breath." As a result, they have become isolated from society. Some have even committed suicide.
Me: Oh.
LP: But Matt, I'm sure that you would be careful. Why don't you think it over and let me know if you would like to work on the structure of some tellurium compounds?

I waited a few days. Then I went back and explained that I thought it would do me more good to work out a more biological structure, something with nitrogens and carbons and oxygens, like an amino acid. (I did not know about phosphorus yet). Without any hesitation, Linus said he thought so, too, and here was a good molecule for me to study: N, N' -dimethylmalonamide. Its two amide groups ought to be planar, in accord with his prediction from resonance considerations that the amide group is planar. (This was, of course, a critical premise in the protein structures that he and Corey proposed in 1950.) So I determined the structure of N, N' -dimethylmalonamide, learning X-ray diffraction techniques from one of Pauling's post-doctoral fellows, Rafael Pasternak.

That was Linus Pauling's practice: he would assign graduate students to post-docs to learn techniques. It was a happy time for me. I learned something interesting almost every day. From time to time, I would ask Bea Wulf, Pauling's devoted -- and formidable -- secretary, for an appointment to talk with him. She carefully controlled his schedule. But when the time came, Linus always seemed glad to take as long as it took to have a good talk. I do not ever remember having to leave because of something on his schedule. Rather, it was because I ran out of things to talk about and wanted desperately to escape. I remember we talked about Gomperts' interesting curve describing the kinetics of aging; we talked about the electronic structure of fibrous sulfur, about the genetic effects of radiation, about estimating error rates in proteins from error rates in amino acid crystals, and about antibody refolding in a flow gradient as a test of his (erroneous) theory of antibodies. Starting in the middle of 1954 we talked about testing models of DNA replication by labeling with heavy isotopes.

But sometimes Pauling was more available than we graduate students would have wanted. One night, I think in 1954, I heard his characteristic tread in the halls of Crellin Lab. (This is an interesting thing: I was talking to Gary Felsenfeld, to ask him to help me to make up a talk, and Gary mentioned Linus' characteristic tread. I had never thought explicitly about this, but, as soon as Gary said that, I could hear it -- even though it has been what, thirty-five years, since I have heard it. It is something like this: "slippety-slap." It is a kind of determined amble. It was a very characteristic sound, partly because the floors were stone, so the sound would resonate from the floors to the walls and the ceiling.) Anyway, here he is, coming down the hall, and I knew that I had let my structural work on N, N' -dimethylmalonamide -- let us say -- subside, while George Streisinger and I were trying to organize a scientific conference on the biological effects of radiation. In those days this was a hot political subject, although the kind of conference we were trying to organize would have been -- if it had happened -- scientific. But we were unable to do this; by the time a couple of months had passed we had not been able to line up a single auditorium that would allow us to have such a conference. It seemed that the topic was too hot for the auditorium proprietors. It was eating up a lot of my time, and Linus obviously knew, somehow, what was going on.

So, there in Crellin Lab that night, he asked me if I would accompany him to his office. He sat down at his desk and looked at me in that characteristic way of his, over the top of his glasses, and I thought "Oh, boy, here it comes!" Instead, he said he wanted to tell me two stories (and again I'll paraphrase): "The first story, Matt, is about Socrates." (It is evidently from The Republic.) "Socrates was once asked, Socrates, what is the proper activity for an old man?' Socrates said, Politics.' Socrates was then asked, And what, Socrates, is the proper activity for a young man?' to which Socrates answered, Science.'" Another searching look over the top of the glasses. "The second story, Matt, is about the great mathematician Karl Friedrich Gauss. Gauss was once asked, Gauss, why are you such a great mathematician?' Answering, Gauss said, I think it is because I never do anything else.'" [Editor's note: at this point, Meselson peered over the top of his glasses.] Well, it was just what I needed. I got right back to work on N, N' -dimethylmalonamide, and, of course, the amide groups were planar.

When N, N' -dimethylmalonamide was finally done, I felt better about talking to Linus about the experiments that Frank Stahl and I had begun, in 1956, in order to find out how DNA replicates. I mention this as a pretext for quoting a remarkable passage in a published lecture that Pauling gave in 1948. This was the Twenty-first Sir Jesse Boot Lecture, at the University of Nottingham. It was entitled "Molecular Architecture and the Processes of Life." Remember, this was 1948. Here is the passage: "The detailed mechanism by which a gene produces replicas of itself is not yet known. In general, the use of a gene as a template would lead to the formation of a molecule not with identical structure, but with complementary structure. It might happen, of course, that a molecule could be at the same time identical to, and complementary with, the template on which it is molded." (In other words, a thing could be a complement to itself.) "However, it seems to me that this case is too unlikely to be valid in general, except in the following way:" (Here are the really amazing sentences.) "If the structure that serves as a template consists of, say, two parts which are themselves complementary in structure, then each of these parts can serve as the mold for the production of a replica of the other part, and the complex of two complementary parts thus can serve as the mold for the production of duplicates of itself."

Well, there you have it, an extraordinary insight. I regret that I never asked Linus if this consideration passed through his mind as he developed the non-complementary model for the structure of DNA that he and Corey published in 1953. Contrary to the impression given in some writings, that 1953 paper did include two interesting biological considerations: the first was that it pointed out forcefully, near the end of the paper, that the (erroneous) three-strand structure for DNA imposed no restrictions on the sequence of nucleotides along the chain and therefore could have enormous specificity, as required for a genetic material; second, that since the nucleotides are on the outside of that model (which of course in real DNA they are not), it would be possible for the sequence of nucleotides to be used as a template to line up the sequence of amino acids of a polypeptide chain. These were some deep biological considerations, and I think it would be interesting to discuss in more detail why Linus came up with this three-strand structure. I think it is all in the first two paragraphs of the paper. It comes directly out of the erroneous crystallography. The data Pauling started with were wrong.

I will conclude this reflection on Linus as an educator by reading a talk that he gave to Swedish University students at the night time torchlight procession that is traditional at the time of the Nobel Prize in Stockholm, when the prizewinners choose one from amongst themselves to address the students of Stockholm at the City Hall. I read this to you because I know he placed a lot of importance on it -- he gave his graduate students copies of it when he came back -- and because what it says is something that I think was very characteristic of his expectations for his students. This is the talk that he gave:

"Young men and women: On behalf of my colleagues as well as myself I thank you for your kind demonstration of friendship and respect. I am reminded of my own students in California. They are much like you. I have observed that students, young people, are much the same all over the world, and that scientists are the same. There is a world-wide brotherhood of youth and science. Perhaps, as one of the older generation, I should preach a little sermon to you, but I do not propose to do so. I shall, instead, give you a word of advice about how to behave toward your elders. When an old and distinguished person speaks to you, listen to him carefully and with respect but do not believe him. Never put your trust in anything but your own intellect. Your elder, no matter whether he has gray hair or has lost his hair, no matter whether he is a Nobel laureate, may be wrong . The world progresses year by year, century by century, as the members of the younger generation find out what was wrong among the things that their elders said. So you must always be skeptical always think for yourself. There are, of course exceptional circumstances: when you are taking an examination, it is smart to answer the questions not by stating what you think is right, but rather what you think the professor thinks is right. Arrhenius discovered that there is danger in being too original in one's doctor's thesis. You have some great problems to solve. The greatest of all is the problem of war and peace. I believe that this problem has been solved, by the hydrogen bomb; that there will never again be a world war, that the knowledge that a world war would mean world-wide destruction (perhaps the end of civilization) will surely now lead to permanent peace, but it is your generation that will have the job of working out the means of preventing disaster by improving the techniques of international negotiations, of developing safeguards against paranoid demagogues who might make nations rabid. You will have this great job to do, and I am confident that you can do it."

These two objectives that Linus talks about at the end seem to me characteristic of his practical approach, as an educator, to political problems, similar in some ways to his approach to scientific problems. So I will conclude by suggesting again that biographers might reach a better understanding of Pauling's life and work by looking more closely at his role as educator.