Paul M. Doty, 91, a Harvard University chemist whose early work helping to assemble the first nuclear bombs led him to become a leading advocate against their destructive use, died Dec. 5 at his home in Cambridge, Mass.

He had congestive heart failure, said his son, Gordon Doty.

Dr. Doty was one the nation’s premier authorities on nuclear arms policy. He advised presidents Kennedy, Nixon and Carter.

“He was a conduit of ideas between the academy and government,” said Joseph Nye, a Harvard professor and a past dean of the university’s Kennedy School of Government.

At Harvard, Dr. Doty founded what is now known as the Belfer Center for Science and International Affairs. Through his more than 40 years on the faculty, Dr. Doty helped nurture the intellectual development of a generation of policy experts, Nye said.

Paul Doty and Wolfgang K.H. Panofsky wait to testify in Washington on April 16, 1975. (James K. W. Atherton/THE WASHINGTON POST)

Dr. Doty’s proteges include several top officials now serving in the Obama administration, including the president’s science adviser, John Holdren; deputy secretary of defense Ashton B. Carter; and undersecretary of defense for policy Michele Flournoy.

The fusion of Dr. Doty’s two main passions — chemistry and nuclear arms control — began in the 1940s when he was assigned to the Manhattan Project, separating uranium isotopes to fuel nuclear explosions.

He quickly realized the atomic bomb’s awesomely destructive capacity and devoted much of the rest of his career to curbing the deployment of nuclear arms around the world.

“Doty was driven by his concern about the potential catastrophes that he and his colleagues helped create,” said Graham Allison, director of the Belfer Center. At Harvard, Dr. Doty helped train a “successor generation,” Allison said, who “might be wiser about ways that these catastrophes might be averted.”

Beginning the 1950s, Dr. Doty used his academic credentials to meet with Soviet Union officials and scientists on unofficial peacemaking missions, a practice known as Track II diplomacy. In all, Dr. Doty made more than 40 trips to the former Soviet Union.

In 1957, he was one of the founding participants of the Pugwash conferences in Nova Scotia that brought together the world’s most eminent scientists to discuss the threat of nuclear weapons during the Cold War.

“The egg was laid — the demonstration that it was possible to have coherent, honest and non-politicized discussions about a common danger,” Dr. Doty told Canadian newspaper the Hamilton Spectator in 2007. “And that gave rise to a whole subculture of East-West discussions outside of government meetings.”

In 1995, the Pugwash Conferences on Science and World Affairs shared the Nobel Peace Prize with Pugwash member Joseph Rotblat “for their efforts to diminish the part played by nuclear arms in international politics and, in the longer run, to eliminate such arms.”

Paul Mead Doty Jr. was born June 1, 1920, in Charleston, W.Va., and grew up in Chicora, Pa.

He was a 1941 graduate of what is now Pennsylvania State University. Soon after, he moved to New York and studied chemistry at Columbia University, where he took classes taught by Nobel prize-winning scientists Enrico Fermi, Isadore I. Rabi and Harold Urey. He once bumped into Danish physicist Niels Bohr in a campus elevator.

He received his doctorate in chemistry from Columbia University in 1944 and joined the Harvard faculty in 1948.

In the late 1950s, he and fellow Harvard chemist Julius Marmur conducted experiments on the structure of DNA that “probed close to the innermost secrets of life,” as Time magazine described them in 1960.

Together, Dr. Doty and Marmur found that two separated strands of deoxyribonucleic acid, or DNA, could be unzipped and put back together without damaging the molecule. The discovery is widely credited with pioneering a number of advances in the study of genetics.

For his seminal work in biochemistry, Dr. Doty became a fellow of the National Academy of Sciences.

In 1968, Dr. Doty founded Harvard’s department of biochemistry and molecular biology. He personally recruited James Watson, the co-discoverer of DNA’s double helix architecture, to join the faculty.

Dr. Doty’s first marriage to Margaretta Gravatt ended in divorce. His second wife, Helga Boedtker, died in 2001.

Survivors include four children Gordon Doty of Cambridge, Mass., Marcia Doty and Rebecca Doty, both of Franklin, N.C., and Katherine Doty of San Francisco; and three grandchildren.

In the 1950s, Dr. Doty served as chairman of the 2,000-member Federation of American Scientists, an international relations advocacy group. His work representing the federation at the Pugwash conferences led Dr. Doty to join President John F. Kennedy’s science advisory committee. In that role, he helped lobby for the nuclear test ban treaty.

Dr. Doty said he believed nuclear arms control required perpetual vigilance. Although “nuclear war is not imminent,” he once said, the key was not “to lose the vision of how absolutely catastrophic nuclear war is.”