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Letter from Linus Pauling to Peter Pauling. March 10, 1953.
Linus first discusses financial matters with Peter in regards to travel, before conveying his flight details to London. He writes that he recently visited UC-Riverside to examine a collection of organic phosphate compounds, and that he has obtained samples of various phosphate diesters, which will be useful in the nucleic acid work. He further discusses the sports car purchase he may make in Europe. Linus then discusses the nucleic acids. He states that it is still not clear to him, through Peter's correspondence and a letter from Watson to Delbrück that Linus has obtained, what the Watson-Crick structure is. Linus mentions that he has solved many of the spatial issues of his molecule by rotating the phosphate groups and notes as well that Rosalind Franklin just wrote to him and that she feels strongly that the phosphate groups must be located on the outside of the molecule. Linus has assumed that the phosphates were located in the center of the molecule all along and further notes that he doesn't think much of the argument of the instability of his DNA molecule due to the packing of negative charges, mentioning other molecules that also have close negative charges. Linus also suggests that RNA could take a similar form to his DNA structure, with some modification. Linus closes his letter by mentioning his recent focus on ferromagnetism.


10 March 1953

Dear Peter:

I enclose a letter to Messrs. Easibind Ltd. Would you write a check for 3 pounds 16 shillings to them, and forward the letter and your check? I enclose my check for $150. Of this sum $125 is your allowance for 1 April. $11.50 is to reimburse you for the check to Easibind Ltd. $13.50 is to cover your expenses – traveling expenses to London, say – in connection with your checking up on a car for us this summer.

Your fine letter arrived yesterday. Mama and I were happy to know that you liked having the seafoam, and also the curtains. I am looking forward now to seeing your room – also to seeing you. I expect to arrive at London Airport at 9:45 A.M. on Friday 3 April. My flight is BOAC 510. I am planning to spend all of my time with you in Cambridge, although it would be, of course, nice, if we could get over to Oxford for a short while, especially to see Dorothy.

Yesterday afternoon Mama and I drove over to Riverside, to look over a collection of 800 organic phosphates that they have there, in the Citrus Experiment Station. I looked them over, and selected four substances for x-ray investigation. Three of them are phosphate diesters. I want very much to find out what the structure of a substance is in which two of the hydrogen atoms of phosphoric acid have been replaced by hydrocarbon groups – presumably the phosphates in nucleic acid are of this type, and so far as I know no one has published a structure determination of any such substance. I think that these substances are more interesting in relation to nucleic acid than the nucleotides themselves, at any rate so far as the phosphate group goes. We have a man, Dr. Rollet, due here next week from Leeds – he is one of Cox’s men – whom we propose to get started on the precise structure determination of one or more of these crystals.

While we were driving over Mama read me your letter, with its advice about cars. I have not yet looked at the letter and the material that you sent, but I shall mention what my feelings are, on the basis of my memory of her reading. First, I am going to be rather short of money this year, what with the trip that we plan this summer (my traveling expenses to and from Germany will be paid by the Unitarian Service Committee, but not the whole family’s), and I am glad to save a thousand dollars on the cost of the car. I like the idea of the Morgan 4-seater – since Mama and I shall be coming over by air, and back also, we shall not have a great deal of luggage (just one big bag apiece), and the 4-seater might be big enough for the three of us. Also, I like the suggestion about the Austin sports model, which I judge would be big enough for us. I should be glad to have you look into the matter of purchasing one or the other of these, and to advise me as to the next step to take. Our plan will be, as I said before, to buy the car in England or France – at present we are getting air reservations to London – and then to drive to Germany, where I am supposed to wander from university to university for 25 days. Then we would drive to Sweden, and back to France or England. We fly home about 1 September. We would put the car up somewhere, so as to have it when we come back about 1 April 1954. I do not know yet how long we should stay then – probably not later than 1 August, because I feel that I shall be anxious to get back and settle down to work on the third edition of The Nature of the Chemical Bond.

Now let me give you some information about nucleic acid. It is not clear to me from your letter and from a letter than Jim Watson sent to Delbruck as to what Watson and Crick have done. I have written to Watson, reminding him that he should be here by 20 September for our protein conference, and also telling him that Delbruck told me that he had mentioned in a letter to him that he had found a beautiful new structure for nucleic acid. I said that I assumed that his structure was not just a variant of our – three polynucleotide chains with the phosphate groups in the middle – but something significantly different. I also mentioned that we have found it necessary to make a little change in our structure. I had tried to loosen the structure up a bit by small changes in the atomic positions, but without success. Then Verner Schomaker suggested that the phosphate groups be rotated through 45° about their vertical axis. This seems to do the job. At present I am trying to evaluate precise parameters for the new structure. One difficulty is that I am not sure that the x-ray data require that the polynucleotide helixes have 24 residues in 7 turns. They seem to me to indicate this, but not to prove it. With the new structure there is, I think, the possibility of a somewhat different number of residues per turn than 3.43.

I have just received a letter from Miss Franklin. She said that she had seen the manuscript – I judge the one that I sent to you. She also said that she had written up their work in three manuscripts, and given them to Professor Randall, who had not looked at them yet, however. She said that she moves this week to Birkbeck College. She said that she hoped that Randall would approve sending copies of the manuscripts to me later on. She said that they had concluded that the data indicated that the phosphate groups are not along the core of the molecule, but are on the outside. I am pretty skeptical about their being able to prove this – I have just had to assume that the phosphate groups are in the center, because I do not see much evidence from the x-ray data one way or another. I told her that if she wanted to see me (she said that she would like to talk with me while I am in England) she could come up to Cambridge during the weekend. If you make any plans for me that would interfere with my seeing her on any day you might let her know what the plans are. I don’t think that I have ever met her – I would much rather see Miss Cowan, whom I have met; in fact, she used to attend my lectures at Oxford.

Alex Rich has been getting much better fibers of nucleic acid (sodium thymonucleate) than we had before.

I don’t think much of the argument that our structure has to be ruled out because there is too much negative charge along the axis. For example, phosphoric acid can lose three protons, assuming a triple negative charge, in alkaline solution, even though the three charges are all within 2.5 A of one another. The second acid constant of oxalic acid is only about 10-2 times the first, even though the two charges on the oxalate ion are similarly close to one another. The small distance between the negative charges on the nucleate ion should, of course, show up in the acid constants, as shown by the titration curves. I have not looked into this matter recently, but I think that the acid constants are somewhat smaller – about pK 4-5, say, instead of pK 2 – than the acid constant for phosphoric acid diester. However, you may feel better about the new structure. In the new structure one oxygen atom, not esterified, of each phosphate group is close to the axis – only 1.5 A from the axis – and close to two other equivalent oxygen atoms. The other non-esterified oxygen atom of each phosphate group is, however, rather far out, 4 A from the axis. This oxygen atom could, then, be in contact with a sodium ion, or even with the positive ion group of the protein side chain, such as the guanidinium ion of an arginine residue in clupein.

Also, I may say in answer to the statement in your letter that I do not see why the presence or absence of a hydroxyl group on carbon atom 2’ of the furanose ring makes any difference in our structure. There is room enough for the oxygen atom (the hydroxyl group), so that the structure is a possible one for ribonucleic acid as well as for deoxyribonucleic acid. One of them, ribonucleic acid, might well, of course, be stabilized through the formation of an extra hydrogen bond for each residue. We have been hoping to get some radial distribution functions for sodium ribonucleate and sodium deoxyribonucleate, in order to decide whether the structures are the same or not, but we have not succeeded in getting anybody to work on this problem.

I was glad to hear the news (confidential) about Bragg and the Royal Institution. I hope that he does decide to accept. I said last summer, in talking with people in England, that I thought that Bragg was the only man in England who would really be a good choice as director of the Royal Institution, and that I thought that he might be willing to resign from the Cavendish a bit before reaching retiring age, in order to take the job. It is true that if the Medical Research Council unit moves to the Royal Institution you might have some difficult decisions to make.

During the last month I have been working on a theory of ferromagnetism. I am going to try to write it up tomorrow. I feel for the first time in my life that I understand ferromagnetism, and the new theory permits me to calculate the saturation magnetic moment per atom for iron – this has never been possible with any earlier theory. The calculated value, which makes use of spectroscopic date only, is 2.20 Bohr magnetons per iron atom, in excellent agreement with the observed value, 2.22. This work will be published in the Proceedings of the National Academy of Sciences. I can explain it to you when I see you.

Love from

[Linus Pauling]

P.S. Let me know if you would like to have a copy of the ferromagnetism manuscript.

P.S. to letter to Peter Pauling, dated 10 March 1953

I don’t think that I have mentioned to you that I got my passport, with only minor difficulty. It is good for one month, 25 March to 25 April, and valid only for England and Belgium. Also, Linda wrote to ask if anything more had happened in the Budenz matter. Nothing more has happened. Budenz has not, so far as I am aware, taken any action in response to my calling him a professional liar and saying that he ought to be prosecuted for perjury.

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