Emil L. Smith, 97, who pioneered the process of determining the structure of proteins and led the first scientific delegation to China, died May 31 in Los Angeles from complications of a heart attack two months earlier.

"Emil Smith was one of the true pioneers in the development of protein chemistry, particularly in the immediate decades following World War II," said biochemist Ralph Bradshaw of the University of California, Irvine. His work "was instrumental in providing some of the earliest evidence for Darwinian evolution" of proteins.

Based in large part on this work, Emile Zuckerkandl and Linus Pauling proposed the idea of a molecular clock, arguing that changes in proteins - and hence in the genes that serve as their blueprints - occur at a fairly constant rate. Thus, rhesus monkeys and humans diverged from a common ancestor much more recently than did humans and horses.

In 1963 - after work at Cambridge University, E.R. Squibb & Sons in New Brunswick, N.J., and the University of Utah - he was recruited to chair the department of physiological chemistry at UCLA's then-new school of medicine, promptly renaming it the department of biological chemistry to reflect the field's importance to medicine. The department "immediately jumped several notches in stature," said Irving Zabin, a professor emeritus.

One of Mr. Smith's proudest moments was his selection by President Richard M. Nixon to lead the first scientific delegation to China, in 1973. The group met with Premier Chou En-lai and helped to establish communication between scientists in the two countries for the first time. - Los Angeles Times