Rose died in his sleep early on Tuesday in Deerfield, Massachusetts, said spokeswoman Janet Wilson of the University of California, Irvine, where Rose had been a researcher.

Rose had a “formidable intellect and unwavering curiosity about fundamental biological and chemical processes that are the foundation for life,” UCI Chancellor Howard Gillman said in a university statement.

Each human cell contains about 100,000 different proteins, which carry out jobs such as speeding up chemical reactions and acting as signals.

Rose, along with Israelis Aaron Ciechanover and Avram Hershko, won the Nobel for discovering how plant and animal cells marked old and damaged proteins with a “kiss of death” molecule the polypeptide ubiquitin. The proteins are then chopped to pieces.

Rose was born in Brooklyn, New York, on July 16, 1926, and spent much of his career as a researcher at the Fox Chase Cancer Center in Philadelphia. His Nobel-winning work was done there in the late 1970s and early 1980s.

Rose’s intelligence and knowledge were “in the stratosphere compared to the rest of us in the field,” and he was always willing to provide hands-on help to students and researchers struggling with experiments, Ralph Bradshaw, a long-time friend of Rose’s and a UC Irvine professor emeritus of physiology & biophysics, told the school.

On the day that Rose was announced as a co-winner of the Nobel, “he tucked two test tubes in his shirt pocket and that night quietly slipped into a building named after another UCI Nobel laureate, Frederick Reines, where he used the university’s powerful mass spectrometry facility to analyse the contents,” the university statement said.