DPR/MB 9th December 1952.

Professor Linus Pauling, Sc.D., Gates and Crellin Laboratories of Chemistry, California Institute of Technology, Pasadena 4, California, U.S.A.

Dear Pauling,

Thank you very much indeed for the useful information about punched cards and the Sherman-Cross strips. Now that I know exactly what is available, I am going in to the question of practicable computing procedures over here. We are less blessed with the latest I.B.M. machines than you. There is just a possibility of using an electronic digital computer and I am exploring this avenue first. So that, for the moment, I do not have to trouble you further with regard to the punched cards but I will certainly write again if it seems that I need them.

By the way, might I have reprints of your papers with Shaffer and Schomaker in J.Chem. Phys. 1946, 14, 648 and 659, if any are still available?

I am very glad to learn that you have now fixed a date for the Protein Conference. This ought to be a great success and I am eagerly looking forward to it. I shall certainly be able to come to it, but whether I shall be able to stay on afterwards will rather depend on developments here. The whole future of this Laboratory is now under discussion, including my place in it, and I shall have to await the results of these deliberations before

Professor Linus Pauling. -2- 9th December 1952.

knowing whether I can take up your very kind offer. Would it be possible for me to delay a decision about it until the Spring?

We have gone no further with the γ-helix or the 3-chain collagen model, except to satisfy ourselves that a large proportion of proline residues is incompatible with the former.

It is as well to have an independent check of our serum albumin curve. We are now working with increased resolution and intensity and have confirmed that poly - γ - methyl and poly -Y- benzyl glutamate have your α-helix structure.

With all best wishes,

yours sincerely,

D. P. Riley

A. Rich Linus Pauling 9 December 1952

Preparation of fibers of nucleic acid

I suggest that you try to make well oriented fibers of sodium thymonucleate or other nucleic acid preparations by the use of plasticizers.

The fact that 50 percent relative humidity seems to be required to give good fibers suggests that substances containing hydroxyl groups would be satisfactory plasticizers. I think that you should try adding a little glycerine to the solution. Perhaps ethylene glycol or diethylene glycol would be worth trying. In fact, perhaps all of these substances should be added to the same preparation - mixed plasticizers often are more effective than the individual plasticizers.

As to other substances, urea and salicylic acid and guanidinium ion might all be worth trying.

There is a possibility that dibutyl phthalate would be useful.

For one preparation you night try putting all of these things in the solution, with the nucleic acid, the plasticizers being added in rather small amounts.

I am also asking Dr. Marsh to make a spectrometer investigation, and to calculate a radial distribution function. Would you turn over to him about 0.5 g of a preparation, for this purpose. If your powder photograph of the sodium thymonucleate taken directly from the bottle gives as good a powder photograph as the recrystallized material, I suggest that you give him a sample of the material from the bottle. Small amounts of impurities would not be important.

Dictated by Linus Pauling

Signed in his absence:W

cc: Professor Corey L.P.