Dear Dr. Pauling,
Thank you for the dimensions of the proline ring and your comments about the collagen
model which Francis and I have formulated.
We are indeed aware of the disadvantages which you describe, especially those dealing
with the deficit of Hydrogen bonds. However, if the sequence –gly–pro–hypro occurs
systematically in collagen, one must of necessity lose hydrogen bonds, neglecting
for the moment those introduced through side chains.
I am enclosing a copy of the manuscript which we sent off to Nature, and which should
appear soon.
We have looked at the infra-red absorption predicted by this model (I should say these
models) and we believe the amide II dichroism would be II and weak. In this determination
we have filled about 1/3rd of the pro sites with proline and 1/3rd the hypro sites
with hydroxyproline. We have also used the transition moments obtained by Sandeman
(Proc. Roy. Soc. A232, IC5, Oct. 1955), which were similar to those obtained by Arthur
Elliott in studying Acetamidizole. However, I quite agree that one should not put
too much weight on the finer features of the infra-red spectrum.
With best regards, yours sincerely,
Alex
