22nd June, 1951

Dear Pauling,

I am very glad to hear about the clearing up of the difficulty about the copper-tin compounds. I have not actually heard from Dr. Shoemaker but I would like to get his account of the structure and to understand how the different arrangements of the atoms accounts for the two forms.

I quite agree that I had in my speech overlooked the Dickinson & Raymond paper of 1922, though I did know of the structure I thought it seemed so long ago, actually before I took up the subject myself, that I had rather treated it as one of the facts of nature.

Actually the hexamethyl-enetetramine structure was quite a special one. Practically unparalleled except in adamantane in crystal structure and therefore the real importance was that Robinson had developed a general method applicable to all unknown structures.

I read your papers with Corey with the greatest interest and I certainly think that you have made the point that it is not necessary that the residues should follow each other along the chain with any regular crystallographic repeats. On the other hand, I am rather doubtful on the basis of Carlisle’s work here, that any structure with as many as 3, let alone 3.7, residues per turn can be fitted into the data for some crystalline proteins such as ribonuclease and chymotrypsin. The number we get by estimation of the number of chains and the periodicities along the chain, in this case about 5.4 A, indicates a figure much more like 2.

I am extremely sorry that you are not going to be at Stockholm and even more so that you won’t be at the Protein Conference that we are holding at Cambridge after it, because I feel that your point of view based on the theoretical chemical information is an essential contribution to the unraveling of the problem. I will probably write to you more about this after these Conferences.

Hope everything goes well with you and yours,

Sincerely,

J. D. Bernal