15 January 1953
Dr. Herbert Kahler
National Cancer Institute
National Institutes of Health
Bethesda, Maryland
Dear Herbert:
I have just seen Dr. Rowen, who told me about some electron micrographs of nucleic acid fibers that yon have made. In particular,
he said that you found, from the length of the shadow, that the molecules are about 20 A in diameter.
Professor R. B. Corey and I have written a paper on the structure of the nucleic acids, which will appear in the February
issue of the Proceedings of the National Academy of Sciences. Our structure is a completely detailed one, with all atoms
precisely located, except that the purine and pyrimidine bases can be attached essentially at random.
It is important in our argument that we know that the molecules are 20 A in diameter. We have quoted your 1948 work, and
work of Ogston as leading to this value from physical chemical data. Also, we have referred to a paper by Williams, showing
by electron micrography that the molecules are roughly this diameter. I think that we should probably refer to your electron
micrographs. If you think that we should, will you give ne some information about your results, and a statement as to how
we should refer to the work — perhaps it will be published before the end of January, and the reference could be given; if
not, we can refer to the journal with the statement "in press."
Our structure accounts nicely for the principal features of the x-ray diagrams. I have been tempted to think that all nucleic
acids have the same fundamental structure.
With best regards, I am
Sincerely yours,
Linus Pauling:W
