John Howard Northrop, a Nobel laureate in chemistry, is best known for his work on the purification and crystallization of enzymes, which regulate important body functions like digestion and respiration. Northrop's studies on the chemical composition of enzymes enabled him to confirm the hypothesis that enzymes are proteins--a discovery that spurred much additional research on these critical catalysts of biochemical reactions. For this discovery, Northrop was awarded the Nobel Prize in chemistry in 1946. In addition to these studies, he also contributed to the development of techniques for isolating--and thus identifying--a variety of substances, including bacterial viruses and valuable antitoxins.
Northrop was born in Yonkers, New York, on July 5, 1891, to John Isaiah and Alice Belle (Rich) Northrop. The Northrops hailed from a long list of notable ancestors; well-known relations include the Reverend Jonathan Edwards, president of Princeton University in 1758. Prior to his son's birth, Isaiah Northrop was killed in a laboratory fire at Columbia University, where he taught zoology. Alice Northrop, a biology teacher at Normal (Hunter) College, influenced her son's interest in zoology and biology. John Northrop received a B.S. in 1912 from Columbia University, where he majored in biochemistry. He continued his studies in Columbia's chemistry department and was awarded an M.A. in 1913 and a Ph.D. in 1915.
In 1915 Northrop accepted a position in the laboratory of Jacques Loeb at the Rockefeller Institute for Medical Research (RIMR). Loeb, an experimental physiologist, headed RIMR's laboratory of general physiology. There Northrop studied the effect of environmental factors on heredity through experimentation with Drosophila (fruit flies Drosophila). He developed a method for producing Drosophila free of microorganisms, which revolutionized studies that investigated factors affecting the flies' lifespan. Using these flies, Northrop and Loeb demonstrated that heat affected the life and health of the flies--not light or expenditure of energy, as previously believed.
Northrop's work in Loeb's laboratory was interrupted by the advent of World War I. At that time he became involved with research geared toward wartime concerns. Northrop developed a fermentation process for acetone that was used in the production of explosives and airplane wing coverings. As a result of these efforts, he was commissioned a captain in the U.S. Army Chemical Warfare Service. He was subsequently sent to the Commercial Solvents Corporation in Terre Haute, Indiana, to oversee the plant development of acetone production.
Although Loeb and Northrop remained close associates, Northrop was ready for independent work upon his return to the institute in 1919. At this time he studied the digestive enzymes pepsin and trypsin ; these studies continued throughout the 1920s and 1930s, but Northrop was also interested in a myriad of other scientific investigations. He studied vision in the Limulus crab; with RIMR colleague Moses Kunitz he analyzed the chemical composition of gelatin; and he worked with Paul De Kruif on bacterial suspensions.
Shortly after Loeb's death in 1924, Northrop transferred to the institute's Princeton, New Jersey, department of animal pathology; at this time he was made a full member of the institute. The animal pathology department was opened in 1917 to study basic research in animal diseases and later expanded in 1931 to include a department of plant pathology. Inspired by the work of James B. Sumner, who had isolated and crystallized an enzyme called urease, Northrop continued his studies of the protein-splitting enzymes pepsin, trypsin, and chymotrypsin ; he eventually isolated and crystallized all three substances. In 1929, Northrop and M. L. Anson developed the diffusion cell, a relatively simple means for isolating materials. In 1931, with Kunitz, Northrop validated the usefulness of the phase rule solubility method of studying the purity of substances, which tests for the homogeneity of dissolved solids. By applying this testing method to crystalline pepsin, chymotrypsin, and trypsin, he corroborated Sumner's controversial belief that enzymes were proteins. The research of this period was presented in Crystalline Enzymes (1939), written by Northrop, Kunitz, and Roger Herriott.
Northrop's investigation of bacteriophages (viruses that attack bacteria) began in the 1920s, but did not flower until the 1930s. He and associate Wendell Stanley applied their techniques for isolating enzymes to crystallizing the tobacco mosaic virus --isolation being the first step in determining the chemical composition of any substance. From 1936 to 1938 Northrop examined the chemical nature of bacteriophages and successfully isolated purified nucleoprotein (protein plus DNA and RNA) from cultures of Staphylococcus aureus, the bacteria that causes boils; this finding was one of the earliest indications that nucleoproteins are an essential part of a virus . Using his ability to isolate and crystallize substances, in 1941 Northrop produced the first crystalline antibody, for diphtheria. He would later, with W. F. Goebel, produce an antibody for pneumococcus.
With the start of World War II, Northrop was once again called on to become involved with government research undertaken at RIMR. In 1941, RIMR and the U.S. Office of Scientific Research and Development (OSRD) initiated the investigation of lethal gases used in battle. One of Northrop's biggest wartime achievements was developing the Northrop Titrator and the portable, battery-operated Northrop Field Titrator. These devices measure the concentration of mustard gas in the air at some distance from the gassed zone. The Northrop Titrator is considered an important prototype for subsequent development of the more sophisticated defensive instruments used in chemical warfare today.
In 1949, RIMR's Princeton facility closed, prompting Northrop's move to the University of California, Berkeley. During his tenure as visiting professor, Northrop maintained his association with RIMR and was named professor emeritus in 1961. While at Berkeley, Northrop continued his work with bacteriophages. He conducted research on the life cycle of B. megatherium cells from their normal stage to that of a phage. He also investigated the origin of bacterial viruses and found that they were mutations of normal cells.
In addition to the Nobel Prize, which he shared with Stanley and Sumner, Northrop was also awarded the W. B. Cutting Travelling Fellowship and the Stevens Prize of the College of Physicians and Surgeons of Columbia University, and he was elected to the National Academy of Sciences. Beginning in 1924, he also served on the editorial board of the Journal of General Physiology, an association that spanned a sixty-two year period.
Northrop retired from Berkeley in 1959 and moved to Wickenburge, Arizona, where he died on May 27, 1987. He left his wife, Louise Walker, whom he married in June, 1918, and two children, Alice Havemeyer and John.
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