The 288-residue structure that Wrinch proposed was attractive in part because it fit
with a principle that other researchers believed might underlie the structure of all
proteins. The case had been put forward by Max Bergmann, an expatriate German researcher
and respected biochemist, along with the same Carl Niemann who helped Pauling with
his paper. The Bergmann-Niemann hypothesis seemed to show how a field as puzzling
as protein structure might be explained with simple mathematical equations. They postulated
that all proteins were formed from a certain number of amino acid residues expressed
as powers of the integers two and three. This gave rise to the 288 amino acids in
a cyclol cage, and its multiples, which were observed in fibrin (576 amino acids)
and silk (2,592 amino acids). The simple formula 2n x 3m might, they thought, help unlock the secrets of proteins. "Everyone who is familiar
with the history of protein chemistry may feel somewhat amazed on being confronted
with a simple stoichiometry of the protein molecule," Bergmann wrote.
Pauling was not amazed. He was skeptical. He could see no good chemical reason for
the Bergmann-Niemann formula, or for the 288-residue basic unit; while some proteins
fell into the pattern, others, it seemed to him, did not. In any case, he distrusted
the whole idea of "magic numbers" designed to explain natural phenomena. His work
on crystal structures showed, if anything, how many ways nature could find to put
things together. There was a sort of philosophical attraction in linking simple equations
to natural phenomena, and in some cases these approaches worked, but Pauling did not
see any chemical reason why it should work for proteins.
Then, in 1939, an associate of Bergmann's named William Stein showed definitively
that some protein data could not be accommodated by the Bergmann-Niemann principle.
Faced with the new information, even Bergmann was forced to abandon his idea. From
that point on, protein researchers were freed to look for new answers that did not
rely on magic numbers. And Pauling would lead the way.