Betsythedevine · CC BY-SA 4.0

Edmond Fischer, with his longtime collaborator Edwin Krebs, worked out how reversible phosphorylation acts as a molecular switch, turning proteins on and off to regulate processes throughout the cell — a mechanism now understood to underlie everything from metabolism to disease signaling. The discovery earned the pair the 1992 Nobel Prize in Physiology or Medicine. Fischer later served as honorary president of the World Cultural Council from 2007 to 2014, and at his death in 2021, at age 101, he was the oldest living Nobel laureate.