On the Structure of the Protein Molecule

UNORTHODOXY in science should always be welcomed and given a hearing: how else would the theory of phlogiston have been relegated to limbo? Unorthodoxy, however, must be sure that its own eye is clear of beams while it is decrying the motes in the eyes of the orthodox. Troensegaard's researches in protein chemistry have now been going on for about twenty-five years. He points out, quite correctly, that to boil a protein for many hours in a fierce reagent like 20 per cent hydrochloric acid may be to destroy the very structures which the chemist is seeking. His alternative line of attack appears, however, to be even more violent. To start with, his proteins are thoroughly dried, even to the extent of storing over phosphorus pentoxide. Proteins exist naturally in aqueous surroundings, and when they are isolated from these, some 'bound water' goes with them, and only under very limited experimental conditions can it be removed without turning the native protein into something else. Troensegaard finds that if dry gelatin is dissolved in anhydrous methanol-potassium hydroxide and neutralized with ethyl acetate, the total amount will be precipitated if more dry methanol is added. He argues, therefore, that the gelatin has formed a colloidal solution ; hence there cannot have been any great splitting up of the molecule. True, but there can have been other changes, such as ring closure following the removal' of bound water from active centres in the gelatin molecule.