Sending in that first paper opened the floodgates. One month after submitting the
manuscript on the alpha and gamma helixes, on March 31, 1951, Pauling and Corey followed
it with a full broadside, mailing PNAS no fewer than seven protein structure manuscripts in a single bundle. It was an audacious
move. They offered more precise details about the alpha and gamma helixes, descriptions
of the structures of synthetic polypeptides, pleated-sheet structures, and ideas about
more complicated proteins like collagen and hemoglobin, hair and muscle, and feathers.
It was a bravado display of Pauling's model-building methods. The papers offered maps,
detailed down to the individual atoms, of structures most workers in the field believed
would not be solved for decades.
It would take months, perhaps years of review before the validity of the work could
be confirmed. Max Perutz, one of Bragg's researchers, read all the Pauling-Corey papers
in a single Saturday morning and set off immediately for his laboratory. If Pauling
was correct and there were 3.7 angstroms in every turn of the alpha helix, then each
individual amino acid should account for roughly 1.5 angstroms of a helix's length.
That distance – the length accounted for by each amino acid – was very small, so small
that it would take special experiments to show it on x-ray diffraction patterns. But
it would be worth it to try, Perutz realized, because of all the many structures proposed
for keratin, only Pauling's would create that particular spot. It would be a sort
of fingerprint for the alpha helix. So Perutz got a strand of horsehair, set it up
in an x-ray apparatus, loaded a piece of film curved in a way to catch the predicted
reflections, and shot it. He developed the film and scanned it. There, just where
he would expect it, was a fuzzy spot far on the margins of the film, an indication
of a structural repeat every 1.5 angstroms. This was interesting, but it was not enough.
So Perutz set up a porcupine quill and shot it. There was the spot. Then he found
it in synthetic polypeptides. Then in hemoglobin. With growing excitement he went
back into his files and found it on some old protein films shot years before, where
the spot had been ignored.
Perutz quickly wrote Pauling, "The fulfillment of this prediction and, finally, the
discovery of this reflection in hemoglobin has been the most thrilling discovery of
my life." He then published his results, concluding, "The spacing at which this reflection
appears excludes all models except the 3.7 residue helix of Pauling, Corey and Branson,
with which it is in complete accord."
Faced with confirmation from his own workers, Bragg conceded at least a part of the
race to Pauling, writing him graciously in June, "Your solution of the alpha-keratin
chain carries conviction. It fits in so beautifully with many facts.... I do congratulate
you most warmly on what I feel is a very real and vital advance toward the understanding
of proteins." Bragg's words, however, were carefully chosen. He held off saying anything
specific about any of Pauling's other structures. In fact the British researchers
could find no evidence of the gamma helix anywhere, and were starting to think that
perhaps it did not exist outside of the imaginations of Pauling and his coworkers.
Neither were they convinced by many of Pauling's other proposed structures, with the
possible exception of the pleated sheets and synthetic polypeptides. The alpha helix
was certainly important, as Bragg had said. Pauling might have won the first leg of
this race. But the alpha helix was not in itself a complete protein, at least outside
of a few fibers, hair, and horn. In most cases it seemed to form a part of other proteins,
a section perhaps. It did not explain the functioning of any of the important proteins.
In the British view, the alpha helix was the no more than the first step in a very