John Howard Northrop

On Ju ly 5, 1981, John Howard Northrop will reach the venerable age of four score and ten. He is active and well for a man of his age but a bit unhappy that his diminished eyesight makes him no longer the skeet supermarksman he once was. The Editors of The Journal of General Physiology and some of Dr. Northrop's friends wish to use this occasion to express their grati tude for his 62-year-long association with the Journal . That association began in 1919, when he published an article in its first volume (1). He joined the editorial board in 1924 and he continues as an Honorary Editor. We also wish to review briefly for the new generation of investigators some of Dr. Northrop's studies which established concepts now taken for granted. (A more complete review of his work was given in the Journal in 1962 [2]). Immediately after receiving his doctorate in Chemistry from Columbia University in 1915, Northrop joined the staff of Jacques Loeb at The Rockefeller Institute for Medical Research. Dr. Loeb was not only a brilliant experimentalist, he was also a keen observer and he liked what he saw in his new associate. Northrop and Loeb enjoyed a happy and productive association until the latter's death in 1924. Soon afterward, Dr. Northrop was made a Member of the Institute. Although he made a number of experimental excursions into a variety of biological phenomena, which led to significant conclusions, Northrop's bestknown contributions were the establishment of the chemical nature of enzymes and his obtaining evidence that bacteriophage contains nucleic acid. He also developed the phase rule solubility method for evaluating protein purity. The nature of enzymes was very much in doubt during the first quarter of this century when several European authorities described them as adsorption complexes between small organic structures and larger, ill defined "carriers." Northrop had become thoroughly familiar with the proteases pepsin and trypsin through his many studies of their kinetic properties. He then turned his attention to their isolation. James B. Sumner of Cornell University had just isolated a crystalline protein with high urease activity, but his evidence that the enzymatic property was linked inseparably to that protein was not strong. When Northrop isolated the crystalline protein pepsin, he deliberately selected a variety of procedures which might have been expected to separate the enzymic activity from the protein if the European model had been correct. When these procedures yielded no separation of the activity from the protein and no change in activity per unit of protein, Northrop was forced to conclude that the two properties were probably inseparable. Working with his highly competent associate, Dr. Moses Kunitz, Northrop found that similar procedures failed to separate the enzymatic activity from the crystalline protein trypsin. Kunitz then went on to find the same for crystalline chymotrypsin,