In a quiet end to a search that baffled investigators for five weeks, Harvard Professor Don C. Wiley was found dead in the Mississippi River on Dec. 20. He was 57 years old.

Wiley , who spent over 30 years at Harvard as first a graduate student and then a professor, was internationally renowned for his work in immunology and structural biology.

For determining the structure of certain proteins that stimulate the immune system, Wiley won two prestigious awards with Higgins Professor o f Biochemistry Jack L. Strominger, the Lasker Award in 1995 and the Japan Prize in 1999.

He “permanently changed the field of immunology” and had “incredible insights on the problems that interested him,” said Mallinckrodt Professor of Immunopathology Hidde Ploegh.

In addition to running a lab at Harvard, Wiley taught both graduate and undergraduate courses for the department of molecular and cellular biology .

“Don Wiley was a brilliant biologist and a greatly admired member of this community,” said University President Lawrence H. Summers in a statement.

Christopher L. Pierce ’02, who took B.S. 56, which Wiley co-taught with Higgins Professor of Biochemistry and Molecular Biology Stephen C. Harrison last spring, said Wiley was known for conveying his enthusiasm about the subject to his students.

“He was interesting, definitely very knowledgeable and he seemed excited to share that knowledge with those in his class,” Pierce said.

Ploegh said Wiley’s enthusiasm extended to his colleagues’ research as well.

“He was very much interested in what his colleagues were doing. Those are the interactions that are the most fun,” Ploegh said.

Wiley, born in Ohio in 1944, earned a degree in physics from Tufts University in 1966 and then completed his graduate study at Harvard.

After earning his Ph.D. in biophysics in 1971, Wiley was appointed as an assistant professor at Harvard and quickly rose to become an associate professor in 1975 and a full professor of biochemistry in 1979.

Wiley was last seen alive at a scientific conference in Memphis on Nov. 15. After finding his abandoned rental on a nearby bridge over the Mississippi River, police investigated the disappearance without any leads until his body was found 320 miles downstream on Dec. 20.

The cause of death has not yet been determined, although an autopsy report is expected soon. Police previously said Wiley may have committed suicide.

Wiley is survived by his wife Katrin Valgeirsdottir, his father Bill, his brother Greg, his sister Pamela and four children.

Funeral services have not yet been scheduled.