Gunther Stent, 84, a DNA pioneer

Gunther Stent, 84, of Haverford, one of the first scientists to confirm the structure of DNA, died June 12 at his home.

Dr. Stent died of pneumonia at the Quadrangle, a retirement community, where he and his wife, Mary Burgwin Ulam, had lived since November.

Dr. Stent, a biochemist who was on the faculty for 40 years at the University of California, Berkeley, agreed to move east when his wife begged him. His proviso was that their new home would be "only Philadelphia."

Ulam said that was because he treasured his membership in the American Philosophical Society, which in 2002 had published his book

The Paradoxes of Free Will.

Years earlier, he and a small collection of scientists, known as the "phage group," had pushed to unlock the mysteries of human genetics. In 1953, group members James Watson and Francis Crick discovered the double-helix structure of DNA, and the following year, Dr. Stent performed experiments with bacterial viruses that confirmed their results.

"Gunther was part of the intellectual glue that kept this small band of pioneers together," Michael Botchan, cochairman of UC-Berkeley's department of molecular and cell biology, which Dr. Stent helped found in 1987, said in a state,emt.

Dr. Stent also led the formation of the campus' department of virology in 1957 and department of molecular biology in 1964.

His 1963 book,

Molecular Biology of Bacterial Viruses,

became a key text in the study of genetics.

In later years, Dr. Stent's interests turned to neurobiology and the relationship between the brain and mental experience. His research on the nervous systems of leeches helped establish the leech as a signature organism in the study of the connections between neural physiology and behavior.

"He got bored with molecular biology, and changed his focus to philosophical matters and consciousness," said Ulam, his second wife, who married him in 2002. Dr. Stent's first wife, Inga, died in 1993.

Dr. Stent was born Gunter Siegmund Stensch in Berlin in 1924. He escaped Nazi Germany in 1939 and joined his sister in Chicago.

Ulam said he wrote about how he was "traipsing through the snow-covered Ardennes forest on New Year's Eve" with a guide, who had helped him flee. At the border before he was able to cross into Belgium, he was briefly stopped by a German frontier police officer, who strip-searched him before allowing him to go.

Dr. Stent received a doctorate in physical chemistry from the University of Illinois in 1948 and worked alongside Watson at California Institute of Technology before arriving at UC-Berkeley in 1952.

Dr. Stent was also known as a scholar of the history and philosophy of biology. He published books on the biology of morality.

Besides his wife, Dr. Stent is survived by his son, Stefan, and stepsons Alexander and Joseph Ulam.

Private services will be held in August and his ashes will be buried in Berlin.