Leon Heppel, a Cornell professor emeritus of biochemistry and a former National Institutes of Health (NIH) scientist who pioneered the study of enzymes that modify RNA, died of complications from a respiratory infection April 9 in Ithaca, N.Y. He was 97.

Born Oct. 20, 1912, in Granger, Utah, Heppel received his B.S. (1933) and Ph.D. (1937) degrees in biochemistry from the University of California-Berkeley. At the University of Rochester School of Medicine, where he received his M.D. in 1942, he discovered that sodium and potassium could cross biological membranes.

During and following World War II, Heppel conducted research at NIH in Bethesda, Md., where he worked with Arthur Kornberg -- a close medical school friend and winner of the 1959 Nobel Prize in physiology or medicine -- on the new field of enzymology (the study of enzymes).

In the 1950s he remained at NIH and studied enzymes involved in the metabolism of ribonucleotides, a component of RNA. His work on the enzyme ribonucleotide phosphorylase and oligoribonucleotides (small groups of ribonucleotides) contributed to the studies of Marshall Nirenberg, another NIH researcher who won the 1968 Nobel Prize in physiology or medicine for cracking the genetic code.

Also at NIH, Heppel went on to study enzymes in the periplasmic space (the space between the inner and outer membranes) of E. coli that are involved in amino acid transport, and he continued those studies when he joined what later became Cornell's Section of Biochemistry, Molecular and Cell Biology (BMCB) in 1967 (now, with the Section of Genetics and Development, it is the Department of Molecular Biology and Genetics).

In his later years at Cornell, Heppel researched ways to inhibit the growth of cancer cells and began studying various physiological effects of ATP, the molecule that is a universal energy source in living cells.

Heppel won several awards in his career and was a member of the National Academy of Sciences and the American Academy of Arts and Sciences.

Heppel had a lifelong interest in the fine arts, ranging from music to painting. He was famous at Cornell for inserting "identify the painting" quizzes into his biochemistry lectures, and he requested that any donations in his memory be made to the Cayuga Chamber Orchestra in Ithaca, N.Y.

Heppel was predeceased by his wife of 62 years, Adelaide; he is survived by two sons, their spouses and three grandchildren.