A Discussion on the Protein Molecule, 17 November 1938. Opening Address

The proposal of the subject for this discussion is in itself a remarkable thing and a symbol of the spirit of this meeting. A few years ago the proposal would have looked preposterous. Proteins were known as a mysterious sort of colloids, the molecules of which eluded our search. What is it then that has happened in these years? Why is the most distinguished scientific society of this country inviting a discussion on the protein molecule? The brilliant work on inorganic colloids, especially on gold sols, by Zsigmondy and others had shown that the mass of the particles of these colloids changed continually with the conditions of their formation. The particles had no individuality from the quantum point of view—therefore they were not molecules although they obeyed the same laws of thermal motion as the molecules. Now the proteins behaved in many respects like inorganic colloids, were held back by membranes, diffused very slowly, etc., and one therefore concluded that the protein particles were not molecules. Another line of thought led to the same conclusion. In spite of all their efforts and the wonderful achievements in other fields the organic chemists were not able to synthesize molecules of a mass approaching—even in a modest way—that of the protein particle. Giant molecules, therefore, were supposed not to exist—only clusters of ordinary small molecules forming particles of undefined mass.