Dr. Margaret Oakley Dayhoff, 57, the associate director of the National Biomedical Research Foundation at the Georgetown University Medical Center, died of a heart attack Feb. 5 at her home in Silver Spring.

Dr. Dayhoff, a biochemist, was a professor at the medical center and a recognized authority in medical computer technology. She was the author of the Atlas of Protein Sequence and Structure, a standard work on proteins and DNA sequences that has been computerized. It has applications for research in many fields, including genetic engineering.

Proteins are sometimes described as "living fossils." By comparing proteins of different organisms, researchers can better understand evolution and similar scientific processes. Dr. Dayhoff herself was known for her work in this field and she made the first evolutionary "trees" based on correlations between proteins and living organisms.

She and her staff also have been credited with a number of other discoveries, including the fact that certain genes normally found in most body tissue are closely related to genes found in many cancer cells.

Dr. Dayhoff was born in Philadelphia. She graduated from New York University, where she was elected to Phi Beta Kappa, and earned a doctorate in quantum chemistry at Columbia University. From 1948 to 1951, she was a research assistant at the Rockefeller Institute.

In 1951, she moved to the Washington area. She was a research fellow at the University of Maryland from 1957 to 1959. She began her career at the National Biomedical Research Foundation in 1960 as associate director and head of the department of chemical biology. She became a professor at the Georgetown University Medical Center in 1970.

She was a member of the American Association for the Advancement of Science.

Survivors include her husand, Dr. Edward S. Dayhoff of Silver Spring; two daughters, Dr. Ruth E. Dayhoff Brannigan of College Park, and Dr. Judith E. Dayhoff Goldberg of San Francisco, and her father, Kenneth W. Oakley of Silver Spring.