Overview

John Howard Northrop (July 5, 1891 – May 27, 1987) was an American biochemist whose laboratory work on purification and crystallization of enzymes provided strong experimental evidence that many enzymes are proteins with defined chemical composition and properties. He shared the 1946 Nobel Prize in Chemistry with James B. Sumner and Wendell M. Stanley for achievements that together helped establish protein chemistry and virology on a molecular footing.

Scientific contributions

Northrop developed and adapted methods for extracting, fractionating and crystallizing biological catalysts so they could be obtained in chemically homogeneous form. By producing reproducible crystalline preparations of several enzyme types, he enabled quantitative studies of activity, composition and stability. These results supported the emerging view, in the first half of the 20th century, that enzymes are individual protein molecules rather than ill-defined colloids.

Methods and impact

His technical approach combined careful control of pH and ionic strength, use of selective precipitants and gradual crystallization to obtain stable preparations suitable for chemical analysis. These methodological advances were influential in protein chemistry, enzymology and early structural studies, and they underpinned later work in biochemistry, medicine and biotechnology where highly purified proteins are essential tools.

Career and appointments

Northrop spent most of his professional life at the Rockefeller Institute for Medical Research in New York City, joining its staff in 1916 and remaining there until retirement in 1961. In 1949 he was elected a Fellow of the American Academy of Arts and Sciences and accepted a professorial appointment at the University of California, Berkeley, where he served first in bacteriology and later in biophysics.

Legacy

Northrop's work is remembered chiefly for its methodological clarity: showing that enzymes could be isolated as pure, crystalline proteins allowed chemists and biologists to treat them as defined chemical entities. This shift in perspective paved the way for later developments in protein sequencing, enzyme mechanism studies and structural biology. The Nobel award he shared in 1946 highlighted how crystallization and chemical analysis could resolve fundamental biological questions.

For further historical or technical context, consult contemporary reviews and institutional histories that discuss early protein chemistry and the transition to molecular approaches to biology. Additional sources and biographical summaries are available through specialist archives and scientific societies linked from institutional pages.