November 2, 1942

Dr. Hugo Theorell

Medicinska Nobelinstitutet

Biokemiska Avdelningen

Stockholm, Sweden

Dear Dr. Theorell:

I was very glad indeed to receive your letter and the four reprints on crystalline horse radish peroxidase. Your results are indeed interesting; I am especially pleased with the clever new micro method which you have developed for the determination of magnetic susceptibility.

I am planning to use your work as the subject of a seminar talk which I shall give in our Institute on Wednesday of next week.

Our work on artificial antibodies is moving along very well. My collaborator Dr. Campbell has shown that artificial antiserum against pneumococous polysaccharide Type I protects mice against Type I pneumonia. The strength of the artificial antiserum is about one-tenth as great as high titer horse serum. In addition to Dr. Campbell, one of our young organic chemists, Dr. David Pressman, and several assistants are working on artificial antibodies and on the quantitative study of immunology. This is the only field of pure science to which I am now devoting any attention.

I shall look forward to hearing the results of your work on the substitution of protohemin in your peroxidase with other hemins. You know no doubt that work along this line was carried on for hemoglobin in our Institute by Dr. Harrison Davies. The most interesting of his results was that when he re-attached protohemes to globin, the resultant hemoglobin had an oxygen partial pressure at half saturation of only a few millimeters of mercury. This may have been the result of failure to re-form the heme-heme links between the four heme groups in the hemoglobin molecule.

Dr. Coryell is now in Chicago, where he is working on leave of absence from his post at the University of California at Los Angeles. I saw him this summer, when I passed through Chicago on the way East. I shall write to him and tell him that you sent him greetings in a letter to me.

With best wishes, and the hope that I shall see you again when the war is over, perhaps through your making another visit to Pasadena, I am

Sincerely yours,

Linus Pauling

LP:jr