William A. DaCosta, 61, a research chemist and an associate professor of biochemistry at Howard University, died Thursday at his home in Arundel on the Bay, Md., after a heart attack.

A former Washington resident, Dr. DaCosta moved to Arundel on the Bay about 15 years ago.

He taught chemistry and biochemistry at Howard from 1947 to 1965, when he became an associate professor of biochemistry.

As a research chemist, he specialized in drug kinetics and metabolism and the physiochemical properties of proteins.

Dr. DaCosta was a member of the executive committee of Howard's biochemistry department and a former director of the university's biochemistry graduate program. He was course coordinator of dental biochemistry there and served on a number of other university committees.

Born and reared in Hamilton, Bermuda, he attended the Berkley Institute, a secondary school founded by his father.

He graduated from Wilberforce University in Ohio and earned a master's degree in organic chemistry from Howard University in 1947. In 1965, he earned a doctorate in biochemistry from Georgetown University.

Dr. DaCosta published numerous papers in his fields and lectured at scientific symposiums.

His professional memberships included the American Association for the Advancement of Science, the New York Academy of Science, the American Chemical Society and the American Association of Chemists.

Survivors include his wife, Frances Mae, of Arundel on the Bay; a son, Michael; a brother, George, and a sister, Vera Lamb, all of Hamilton, Bermuda.