Theoretical chemist Martin Karplus (PhD '54) passed away December 28, 2024, at his home in Cambridge, Massachusetts. Karplus was the recipient of the Nobel Prize in Chemistry in 2013 for work that laid the foundations for the field of computational chemistry, which uses advanced software to predict chemical processes using quantum mechanics. He was the Theodore William Richards Professor of Chemistry, Emeritus, at Harvard University, and former director of the Biophysical Chemistry Laboratory, jointly operated by the French National Centre for Scientific Research and the Université de Strasbourg in France.
Karplus was born in Vienna in 1930, and fled with his parents to the United States in 1938 after the Anschluss, when Austria was overtaken by Nazi Germany. As Karplus tells it in his 2006 autobiographical essay "Spinach on the Ceiling," he came from a family of distinguished doctors and medical researchers, and his family assumed that he too would follow that path as he evidenced an early interest in the family profession. Once gifted with a microscope in childhood, Karplus quickly delved into the world of tiny organisms. He also became an ardent observer of birds and their migration patterns, so much so that, as a high school student, he was invited to join a research team that traveled to the Naval Arctic Research Laboratory in Point Barrow, Alaska, to observe the behavior of nesting plovers.
Attending college at Harvard, Karplus was keen to study biology but reasoned that, in order to do so, he needed a thorough grounding in chemistry and physics. Upon graduation, Karplus debated between studying chemistry at UC Berkeley or biology at Caltech. While visiting his brother at the Institute for Advanced Study in Princeton, Karplus was introduced to J. Robert Oppenheimer, with whom his brother was working. Oppenheimer voted strongly for Caltech, Karplus recalled in his autobiographical essay, calling it "a shining light in a sea of darkness."
At Caltech, Karplus initially studied biology with Max Delbrück (winner of the 1969 Nobel Prize in Physiology or Medicine for seminal work on virus genetics and replication), who, having begun his career as a physicist, switched to biology. But Karplus later decided to move into chemistry and eventually became a student of another Nobel laureate, Linus Pauling (PhD '25). With Pauling, he began work that introduced quantum mechanical calculations to chemical processes. Karplus remembered Caltech for its "intellectual and social atmosphere" and recalled "trips into the desert, as well as frequent parties held at our Altadena house, where [Richard] Feynman would occasionally come and play the drums." At one party, Karplus found Pauling in the backyard collecting snails to take home for dinner.
Karplus completed his PhD at Caltech at the age of 23 and began a postdoc at Oxford, where he explored nuclear magnetic resonance through chemistry. Determined to move to different universities every five years to engage with fresh perspectives, Karplus started at the University of Illinois with the goal of extending his postdoctoral research to further understand the role of nuclear and electron spin magnetic resonance parameters in molecules. There, he developed what became known as the "Karplus equation" for determining the structure of organic compounds. Karplus also had the opportunity at Illinois to begin developing computer programs—delivered via hole-punched paper tapes—to model chemical reactions.
Karplus's use of computing resources for chemistry research accelerated when, in 1960, he moved from the University of Illinois to IBM's Thomas J. Watson Research Center. Cautious about relying on corporate sponsorship, Karplus took the position contingent on simultaneously holding a tenured professorship at Columbia University, where he pursued work on chemical reaction dynamics.
Continuing his five-years-per-institution plan, Karplus moved to Harvard in the mid-1960s, changing his discipline from chemistry to biology. At Harvard and later at the Université of Paris and the Université de Strasbourg, Karplus did his Nobel Prize-winning work "for the development of multiscale models for complex chemical systems," according to the Nobel citation. Karplus and his colleagues relied on computer modeling to calculate the molecular dynamics of biological molecules, a complex problem combining classical mechanics and quantum mechanics. Because of this work, chemical processes that were not thought to be quantifiable turned out to be so. Among other honors, he was a member of the National Academy of Sciences and the American Academy of Arts and Sciences, and a foreign member of the Netherlands Academy of Arts and Sciences and the Royal Society of London.
Over the remainder of his career, Karplus divided his time between the United States and Europe, working with numerous students and postdoctoral researchers who he referred to as his "scientific children."
Karplus is survived by his wife, Marci Hazard, and by two daughters, a son, and a granddaughter.
