May 1, 1951

Prof. N. V. Sidgwick

Lincoln College

Oxford

England

Dear Sidgwick:

I am writing to send our best wishes to you, and to tell you how we are getting along.

The inspiration for writing you came this afternoon when I got down your book CHEMICAL ELEMENTS AND THEIR COMPOUNDS to check up on the chemistry of sulfur, and noticed again the kind reference that you make to me in your preface. When you prepare a second edition of this book I hope that you will allow me to give you my suggestions about every chapter. They would not be numerous - I can't say that I have found anything wrong; but I would like to be of help to you.

I note that you do not say anything about Aten's sulfur pi, which Ephraim discusses in some detail. Apparently Aten thinks that sulfur pi consists of S₄ molecules. Ephraim says that it cannot be S6, because it is more deeply colored than S₆, and also is four times as stable(whatever that means). (I note that Ephraim says that S₆ is about four times as stable as S₄, rather than the opposite.)

Ava Helen and I have just returned from a trip to Philadelphia and Washington, where we attended meetings of the American Philosophical Society and the National Academy of Sciences. We saw Wyckhoff in Washington - I was very pleased that he was elected a foreign member of The Royal Society.

We also stopped at Minneapolis, Urbana, and Detroit, and I spoke at meetings of the local sections of the American Chemical Society at these three places.

No doubt you noticed that Larry Kimpton has been chosen as Chancellor of the University of Chicago. You remember that he was Dean of Deep Springs at the time you visited there about fifteen years ago. The people at Chicago seem to be well satisfied with his selection as the successor to Hutchins. I think that he does not have Hutchins' extraordinary originality, but he seems to show very good judgment in all of his decisions.

Professor Sidgwick

Corey and I are publishing a series of papers on the structure of proteins. One of than is coming out in the April issue of the Proceedings of the National Academy of Sciences, and seven more in the May issue. In these papers we describe quite exactly a number of alternative configurations of the polypeptide chain, in which the interatomic distances and bond angles have the dimensions found for simpler substances, the amide groups are planar, and the carbonyl and imino groups are involved in hydrogen-bond formation. There are only a few configurations discovered so far that satisfy all of these conditions. We have very convincing evidence, from x-ray diffraction photographs, that these configurations are represented in proteins. In our papers we describe the structure of stretched muscle and contracted muscle, and discuss the mechanism of contraction. Stretched hair and ordinary hair have similar structures. Moreover, we have found the structure of two synthetic polypeptides — these, like ordinary hair and contracted muscle, involve a helical configuration of the polypeptide chain. The structure of collagen and gelatin is a very extraordinary one - the molecule consists of three polypeptide chains coiled about one another, like the three strands of a rope, these three chains being held together by lateral hydrogen bonds. Feather rachis also seems to have an interesting structure, involving a sheet of nearly extended polypeptide chains (with, however, a configuration different from that usually assigned to B-keratin), and then a double layer of helical molecules, followed by another sheet, another double layer, and so on. The helical structure of ordinary hair is also present in the hemoglobin molecule. I am sure that these discoveries will introduce a new era in the protein field.

Our boy Peter did not succeed in carrying through his plan of studying at the University of London. He had arranged with Coulson to be accepted as a physics student at King's College, but the University of London would not accept his credentials. (He had finished his sophomore year in physics at the California Institute of Technology.) So he returned home late last September, and began his Junior year here. I think that he will now finish his undergraduate work here, but it may be that he will come to England for graduate work.

I am not sure that we had told you that we have a swimming pool now, just about 30 feet in front of our house. It is elliptical in shape, with axes 20 feet by 46 feet. It is equipped with a heater, and we have kept the water warm enough to permit us to swim nearly every day this winter. I had a swim a couple of hours ago. Since then it has been raining, and, in fact, some hail stones have fallen. We have had a dry winter, and are pleased to have some rain this late in the season.

Professor Sidgwick

I had a letter from Jenkins last month. He wrote that he was hoping to get a full-time job in chemistry, because he was not able to support his family on his theological income. I wrote a testimonial for him, and sent it on to him. Did I ever tell you that in one of the notebooks that he left with me he had written some notes for a talk that he was preparing (perhaps to be given after he returned to Oxford), and he described Southern California as "theologically retrograde."

I am not going to come abroad this summer. I had planned originally to attend the International Congress of Crystallography in Stockholm, but then I changed my mind, feeling that I would rather stay at home. I travel a good bit anyway - next week I am going east to take part in the dedication ceremony of the new DuPont laboratory and of the research building of Massachusetts General Hospital, and on May 25 my wife and I are going to fly to Hawaii, where I shall speak before the local section of the American Chemical Society and other scientific groups. We have not been to Hawaii before, and we are looking forward to our ten days there.

With best regards, I am

Sincerely yours,

Linus Pauling:W