29 January 1953
Dr. Gerald Oster
Polytechnic Institute of Brooklyn
99 Livingston Street
Brooklyn 2, New York
Dear Dr. Oster:
I am glad to have your letter of 26 January, and to know about your interest in
our α-karatin structures.
We shall send you two reprints of the paper when they arrive.
First, as to the form factor of the 7-strand cable, I must say that Crick has written
me that he has evaluated the form factor for a compound helix exactly. His expression
is without doubt similar to the Cochran, Crick, and Vend expression for a simple helix.
I have been interested, however, in approximate expressions that involve less work
I think that the expression that you give for the intensity doesn't apply to our 7-strand
cable. Unless I have misunderstood your work, your expression applies to an aggregate
of 7 cylindrical molecules in parallel orientation, 6 around a central one. The
expression that Corey and I used is an approximate expression for a different ease,
that in which the 6 outer helixes are twisted about the central one.
I have read through your paper on deoxyribonucleic acid - I think that you gave me
a reprint, which, however, I lost, so that I had forgotten about your work until reminded
by your letter. Unless I have misunderstood this paper too, the structure that you
discussed for aggregates of nucleic acid molecules did not involve 6 twisted about
a seventh, but rather 6 arranged hexagonally about a seventh, and with axes parallel
with that of the seventh.
Corey and I have a paper in press now, on the structure of nucleic acids. It is
to appear in the February issue of the Proceedings of the National Academy of Sciences.
The structure is an interesting one, in that it involves three intertwined polynucleotide
chains. Each of the polynucleotide chains has 24 residues in 7 turns of its helix.
All of the polynucleotide residues are structurally equivalent. There is some evidence
in support of the structure. The diameter of the molecule is about 18 A. I am sorry
that we did not remember your paper with Riley, in which you suggest a value of 16
A for the diameter of the molecule. We have already read proof on the paper and
accordingly cannot introduce the reference now.
I should be interested to know what sort of work you are carrying on at the present
time. You mentioned your plan to do some work on proteins in the future; have you
got started on this work, or are you working on nucleic acids, or other substances?