April 2, 1952
Dear Maury:
I thank you for sending me the manuscript of your Letter to the Editor of the J.A.C.S.
Let me say that Dr. Corey and I both feel that it would not be proper for you to publish
this letter, nor for anyone to publish letters or papers about proposed protein structures,
at the present time, without a precise description of the proposed structure. It is
true that up to about a year and a half ago all proposed protein structures were vague,
as is the 11-atom ring helix that you mention in your letter. However, a year and
a half ago Bragg, Kendrew, and Perutz published a paper in which they discussed a
number of proposed structures and gave coordinates for the atoms, to 0.1 A. Then Dr.
Corey and I published our papers, in which, for every structure that we discussed,
we gave tables of coordinates of the atoms, including the beta carbon atoms of the
side chains to 0.01 A. (There is, of course, some probable error to our predicted
coordinates, but at any rate we described the structures as precisely as we could,
and in general we have confidence in our predictions to within a few hundredths of
an Angstrom.)
These precedents show that it is possible for investigators to describe the structures
that they are interested in with sufficient precision to permit them to be reproduced
by other people. I repeat that we feel strongly that the time has now passed when
qualitative discussions of protein structure were acceptable.
It is our opinion that if you want serious consideration to be given to the 11-atom
helical structure you must describe it by communicating the atomic coordinates - I
think that they should be communicated to 0.01 A, together, if you wish, with a statement
of the uncertainty that you associate with your prediction. Once that you have stated
what the structure is that you favor, it can be considered by other people.
There is one place in your letter that seems to me to give the reader a wrong impression
- I may say that you can hardly be blamed for this, since Bamford and Hanby, whom
you are quoting, also wrote their letter to the Editor of Nature in such a way as
to give the reader the wrong impression. The sentence in the middle of page 2 is written
in such a way as to suggest that Dr. Corey and I are responsible for the error (not
a very large one) in the cell dimensions that we assigned to the synthetic polypeptides,
and the letter by Bamford and Hanby gave the reader that impression. However, the
cell dimensions that we reported were based on the dimensions reported by Bamford,
Hanby, and Happey in the Proc. Roy. Soc. (1951), and the errors in our cell dimensions
simply reflect errors in the values that they gave. Then on remeasurement of their
films (or perhaps on measurement of new ones) they found (as has also a man working
in our laboratories) that the fiber-axis lengths reported by them were too long, by
a few percent, and should be reduced to about 5.4 A per turn of the helix. I do not
think that there is any need for you to follow Bamford and Hanby in this effort to
misinform the reader; moreover, for your purpose all that you need to do is to state
that the fiber-axis length per turn is 5.4 A, with the reference (your reference 4)
- or you might want to say that Bamford and Hanby had corrected the values originally
given by Bamford, Hanby, and Happey for the fiber-axis length, which we have interpreted
as the length per turn of the helix.
I might also point out that your letter does not describe the proposed 11-atom structure
even to the extent of saying whether it involves a planar or a non-planar amide group.
Bamford and his collaborators, in suggesting what I assume from your letter to be
the same structure, indicated that it involves non-planar amide groups, as did also
the Bragg, Kendrew, and Perutz prototype. They do not say, however, by how great
an amount the amide group must deviate from non-planarity, nor what the nature of
this distortion is. Dr. Corey and I feel, of course, that they should be criticized
for proposing a structure at the present time without stating precisely what structure
they are talking about.
As to your error in saying in New York that our 3.7-residue helix was identical topologically
with a structure that you had discussed, I was surprised, because I had not remembered
your having discussed just this structure, but I have not, at any time since then,
checked the matter, because it was clear that in any case the similarity was only
topological, and not metrical. I remember that Professor Corey and I felt, when we
published our letter in the J.A.C.S. in 1950, that in your proposal of helical structures
in 1943 you had come sufficiently close, in the 3-residue helix, to our structures
to justify a friendly mention of your work, and for this reason we put in a footnote
saying that "a 3-residue spiral described by Huggins is similar to ours, but differs
from it in essential structural details."
I hope that you will let me know if you decide to withdraw your communication to the
Editor of the J.A.C.S., or to make changes in it.
Sincerely yours,
Linus Pauling
