December 9, 1953
Mr. George Gamow
19 Thoreau Drive
I have been interested to see your letter which arrived in Pasadena just about when
I was leaving, on a trip to Israel.
The problem of the determination of sequence of amino-acid residues in the protein
molecule through complementariness to the nucleic acid molecule is a very interesting
one, Corey and I thought about it in connection with our proposed structure for
nucleic acid (Proc. Hat. Acad. Sci. Feb., 1953) which stimulated Watson and Crick,
who had a copy of the manuscript, to develop their structure, and I know that Watson
and Crick have thought it over too. I feel that a decision has to be made through
the consideration of the shapes of the molecules as to where the amino-acid residues
fit in. The number of possibilities is, as you point out, about enough to explain
the selection uniquely of the residues, in position of about 3.5 Angstrom from one
another along the polynucleotide molecule.
The comment I would make about your number 20 is that I do not see the 12 that you
rule out on the basis that they are D forms. The rhomb is on one side of the nucleic
acid molecule, and there is a polar axis along the molecule if a polypeptide chain
is being built up because the polypeptide chain itself has a polar axis. Hence,
all 32 rhombs are to be considered as different. In fact, I think that the number
should still be multiplied by two.