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substance is in which two of the hydrogen atoms of phosphoric acid have been replaced
by hydrocarbon groups – presumably the phosphates in nucleic acid are of this type,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.
