REC’D MAR 5 1963
HARVARD UNIVERSITY
THE BIOLOGICAL LABORATORIES
16 DIVINITY AVENUE
CAMBRIDGE 39, MASSACHUSETTS
March 4, 1963
Dr. Linus Pauling
Gates and Crellin Laboratories of Chemistry
California Institute of Technology
Pasadena 1, Calif.
Dear Dr. Pauling,
After Jerry Donohue told us that guanine and uracil would be Keto, I made metal models of the bases using published values
when available an otherwise making likely guesses. Then I suspected Broomhead’s guanine structure was not correct in detail
(in particular the angle of the Keto oxygen) but nonetheless I used her bond angles and lengths. Its effect was to make formation
of three good hydrogen bonds unlikely (the 3rd was too long). So we settled for two leaving open the question whether a refined
guanine structure would imply 3 bonds. To my knowledge both Francis and I have accepted the probable existence of 3 good bonds
ever since the appearance of your manuscript with Dr. Corey. Now a student of Alex Rich is completing the structure of a mixed
(1:1) guanine-cytosine crystal. He finds three strong hydrogen bonds confirming your analysis. Why the “Scientific American”
left out ht e3rd bond Is not known to me but I suspect an oversight.
I enclose a copy of my Nobel lecture. It covers my interest in protein synthesis. The DNA structure is treated in Wilkins’
lecture. Crick spoke on the “Code”.
With best regards to your wife and to Linda.
James D. Watson
Enclosure
JDW:mh
