15 January 1953
Dr. Herbert Kahler
National Cancer Institute
National Institutes of Health
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
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