AIR MAIL

April 12, 1946

Dr. William Seifriz

Botanical Laboratory

University of Pennsylvania

38th Street and Woodland Avenue

Philadelphia 4, Pennsylvania

Dear Selfriz:

It is a pleasure to hear from you once in a while, and perhaps some time I shall be able to write an article for the planned JOURNAL OF PROTOPLASM.

I am very much interested in the structure of proto-plasm and I wish that I knew more about the facts which have been gathered that are pertinent.

It is very easy to answer your question, about the Heitler-London bond. This bond is indeed very important in biology, and also in chemistry—it is, in fact, nothing more than the shared-electron-pair bond of Gilbert Newton Lewis, which is itself, of course, the structural feature which is usually represented by the dash of the organic chemist. I have not read Schroedinger's little book, but I am not surprised that he is somewhat confused by these points, because he has never paid very much attention to chemistry.

By the way, I do not think that you should speak of the "Pauling hydrogen bond". The hydrogen bond has a considerable history during the decade or so before 1928, when I became especially interested in it.

Sincerely yours,

LP:par Linus Pauling