Liver juice fractionation and concentration for treatment of pernicious anemia
In 1928, while at Harvard, Cohn was able to concentrate, by a factor of 50 to 100 times, the vital factor in raw liver juice which had been shown by Minot and Murphy to be the only known specific treatment for pernicious anemia. Cohn's contribution allowed practical treatment of this previously incurable and fatal illness, for the next 20 years.
Cohn became famous for his work on blood fractionation during World War II. In particular, he worked out the techniques for isolating the serum albumin fraction of blood plasma, which is essential for maintaining the osmotic pressure in the blood vessels, preventing their collapse. Transfusions with purified albumin on the battlefield rescued thousands of soldiers from shock. After the war, Cohn worked to develop systems by which every component of donated blood would be used, so that nothing would be wasted. On Cohn's office blackboard was inscribed a quotation from Goethe's Faust: "Das Blut ist ein ganz besonderer Saft."
Cohn is also well-remembered for his studies of the physical chemistry of proteins, particularly his general "salting out" equation for protein solubility where is the protein solubility constant and and are constants characteristic of the particular ion S whose concentration is . This equation is identical to the Setschenow solubility equation. Cohn was a long-time collaborator and friend of another important physical chemist, George Scatchard.
A most important book
In 1943, Cohn and John Edsall published Proteins, Amino Acids and Peptides, a book that summarized the known physical chemistry of proteins and deeply influenced succeeding generations of protein scientists.
Personality
Cohn was an excellent project leader, being driven, ambitious, and extremely well organized. He also had a keen taste in people and scientific projects and could sense when either would be successful. The success of the blood fractionation project was due in great part to his management, and he can be considered responsible for saving thousands of lives. Cohn was also selfless in the best scientific tradition. For example, he would often give public demonstrations of the blood fractionation machine, in which he would fractionate his own blood on the stage during the lecture. In one such lecture, at the Instituto Superior Técnico in Lisbon, the machine became blocked and exploded, showering the first few rows of the audience with Cohn's blood. Cohn maintained his sangfroid, however, and continued his lecture without significant interruption. More generally, Cohn drove himself relentlessly and ignored his doctors' advice to cut back on working because of his high blood pressure. However, Cohn was also well known for being harsh and demanding of his subordinates, being something of a martinet.
