10 February 1953

Dr. Jerry Donohue

Cavendish

Laboratory

Cambridge England

Dear Jerry:

I am glad to have the list of interatomic distances. I have found out that Dr. Yakel has a complete list of interatomic distances for the 3.60-residue α helix. He has carried this out through five turns of the helix. I shall ask him to check your list item by item, to see whether he agrees with you. I know that the values that he has differ a little bit from the values used in our calculation, which, however, corresponded to a helix with 3.67 residues per turn, and perhaps the coordinates were a little bit different too. Yakel said that in general the disagreement was only 0.1 A.

I shall look forward to seeing your manuscript on the helical structures.

I enclose a copy of my Solvay Congress paper, without the figures, however - I don't think that the lack of the figures will bother you.

As to the nucleic acid structure, I don't see any reason for it to be unsatisfactory as a structure for the nucleate ion, except of course that the negative charges are closer together than they would be if the phosphate groups were on the outside of the molecule, rather than near the axis. In any ease, hydrogen bonds are pretty weak, and a structure held together just by hydrogen bonds might not be satisfactory. The three chains in our structure are tucked together almost too tightly and bound by the sugar residues.

I don't think that there is any use in trying to decide on substances tor you to investigate in connection with the work on nucleotides, until you get here next fall. I may say that I think, in view of your interest in settling permanently in California, that you should consider a job at U.S.C. seriously. My opinion of bids school has gone up, especially since the new chemistry laboratory has been constructed. The availability of government money for support of research makes the attractiveness of a job at U.S.C. greater than it was before the war. I don't think that there is any possibility of a permanent appointment here at the Institute, and it seems to me that if you are going to take a job at U.S.C. it would be better to take it now than a year later - you would have that much more seniority, for one thing.

Dr. Donohue 2/10/53

I hope that you will be back by 20 September 1953, in order to take part in the conference on the configuration of polypeptide chains in proteins.

I have expressed again to the Guggenheim foundation my strong feeling that the amount of the stipend awarded in some cases, including your case, is too small. I think that the thing for you to do now is to write to the Guggenheim Foundation, sending them a breakdown of your expenses somewhat like the one that you have enclosed with your letter, pointing out that the cost of living and traveling has turned out to be greater than you had anticipated, and asking if an additional grant can be made to you. I do not know what will be done - I am not on the board this year.

I shall be in Cambridge from Saturday to Tuesday, according to present plans, and I should have time for a good talk with you.

With best regards, I am

Sincerely yours,

Linus Pauling:W

10 February 1953

Prof. A. R. Todd

Merton Hall

Cambridge

England

Dear Alex:

I enclose a clipping from the New York Times - you may not have a copy of it.

I sat pleased to learn about the work that you have done. It looks like the outstanding work in organic chemistry during recent years. We all send our congratulations to you.

Also, I hope that you have enjoyed your visit in Australia.

I should look forward to seeing you when I stop in Cambridge, 4 to 7 April, on my way to the Solvay Congress.

Please give my love to Alison.

Cordially,

Linus Pauling:W

ART/JS 10th February, 1953

Professor Linus Pauling,

Gates and Crellin Laboratories,

California Institute of Technology,

Pasadena 4,

U.S.A.

Dear Linus,

On my return from India I found your letter of 19th December awaiting me with the exciting news that you think you have got the structure of the nucleic acids. I shall be most interested to get more detail of it and I hope you will keep me posted. Certainly if there is any help we can give you we will be only too glad to do so.

I have seen Bragg and Cochran about this question of nucleotide examination because I agree with you that we are sorely in need of data on these substances. Cochran is actually doing an examination of adenylic acid b which he got from us, and he also has a sample of muscle adenylic acid which he is looking at in a preliminary way. I understand that these nucleotides are very difficult subjects for study and I do not think that Cochran is likely to tackle more than these two in the near future. I would say then that if you keep off the phosphates of adenosine you would not be duplicating their present work.

As regards other people who might be doing something of the sort, Zussmann, who was here in the Cavendish and then went to Manchester, took away with him a sample of the crystalline barium salt of uridine-5' phosphate which we gave him. We have not heard from him since and so I do not know whether he is working on it seriously or not. Furberg in Oslo is also supposed to be working on cytidylic acid b and he was at us some time ago for a sample of ribose-5 phosphate, but again I know nothing about his progress.

So far, of course, we have been the chief suppliers of these substances although a number of then can probably be got in the States. In addition to those above mentioned, the following ribonucleotides are crystalline and we either have them available or could get them for you:

uridylic acid b and cytidine-5' phosphate,and cutidylic acid a

Professor Linus Pauling page 2

I have wondered, however, whether, since as far as I know no-one is doing anything about the deoxyribonucleotides, and since we have been synthesizing them and it is most unlikely that anyone else can produce them, you might wish to look at some of them. We have so far made both the 3' and 5' phosphates of thymidine and deoxycytidine, and we are at present preparing the corresponding substances from deoxyadenosine and deoxyguanosine. I wonder if you would let me know what things you think you would like to have, and as soon as I hear from you I can get samples of them sent off.

You mention ATP in your letter. Actually we have never been able to crystallise free ATP, and the only crystalline derivative we have is acridine salt; the substance itself and its barium salt seem to be resolutely amorphous. At the moment I do not think we have any good preparation on hand but we have a main in the lab, who is making some ATP, so if you would like to have it I can let you have some in the form of a salt when it is ready.

I look forward to hearing from you soon and meantime send best regards to all of you.

Yours,

Alex