January 21, 1953
Dr. Linus Pauling
California Institute of Technology
Gates and Crellin Laboratories of Chemistry
Pasadena 4, Calif.
In reply to your letter of January 15, the paper "The Electron Microscopy of Sodium
Desoxyribonucleate" by H. Kahler and B. J. Lloyd, Jr. is in press in Biochimica and
Biophysica Acta. Enclosed is an abstract presented before the Electron Microscope
In this paper we conclude that the diameter of nucleic is 15 + 5 Ǻ. Most of our
measurements were actually within the range of 15 + 2 Ǻ, but there is some uncertainty
about the exact place where the shadow ends. An arbitrary decision has to be made
in making the measurement, and since this decision made lead to a systematic error
of a couple Ǻ we leaned backwards and simply put a round figure 5 Ǻ as the overall
error. In any event, I would be surprised if the diameter is greater than 20 Ǻ.
Our photographs have one important advantage over those of Williams in that the fibers
tend to lie in a flatter position on the substrate film, whereas in his technique
most of the fibers are partly off the film due to the freezing process. However, it
was very satisfying to find that we both got the same value in completely independent
I am very much interested in your paper and should like to receive a reprint as soon
With best wishes.