Roger Y. Tsien speaks in 2008, the year he shared the Nobel Prize. (Fredrik Persson/AP)

Roger Y. Tsien, who shared the 2008 Nobel Prize in chemistry for helping develop fluorescent markers that could tag cancer cells or track the advance of Alzheimer’s disease in the brain, died Aug. 24 in Eugene, Ore. He was 64.

The death was announced by the University of California at San Diego, where Dr. Tsien was a professor. He apparently died while on a bike trail, the San Diego Union-Tribune reported, but the cause of death had not been determined.

Dr. Tsien was a professor of pharmacology, chemistry and biochemistry at UC San Diego’s medical school for 27 years.

In 2008, he shared the Nobel with Osamu Shimomura and Martin Chalfie for helping turn green fluorescent protein from a jellyfish into a research tool that could literally illuminate everything from brain cells to bacteria.

Dr. Tsien helped create markers that, under ultraviolet light, glow in a wide variety of colors. Researchers use the markers to track cellular processes.

“Our work is often described as building and training molecular spies,” Dr. Tsien once said, “molecules that will enter a cell or organism and report back to us what the conditions are, what’s going on with the biochemistry, while the cell is still alive.”

A version that surgeons can use to differentiate cancerous tissue from healthy tissue is in development.

“I’ve always been attracted to colors,” Dr. Tsien told the Union-Tribune in 2008. “Color helps make the work more interesting and endurable. It helps when things aren’t going well. If I had been born color­blind, I probably never would have gone into this.”

Roger Yonchien Tsien was born in New York City on Feb. 1, 1952, to Chinese immigrants. While growing up in Livingston, N.J., he began sketching chemistry experiments at age 8 and earned his first Boy Scout merit badge in chemistry. At 16, he won the national Westinghouse Science Talent Search with a project analyzing how metals bind to thiocyanate.

He graduated from Harvard with a bachelor’s degree in chemistry and physics in 1972, and he received a doctorate in physiology in 1977 from the University of Cambridge in England.

He remained a research fellow at Cambridge for several years and was on the faculty at the University of California at Berkeley for much of the 1980s. He joined UC San Diego in 1989.

Survivors include his wife, the former Wendy Globe. A more complete list of survivors could not immediately be determined.