American molecular biologist who was corecipient of the 1978 Nobel Prize in medicine with Hamilton Smith and Werner Arber for the discovery and use of restriction enzymes. Restriction enzymes are proteins that cut DNA chains. Nathans's work allowed researchers to modify the DNA molecule and paved the way for new innovations in biotechnology. Biotechnology companies use his work to make synthetic versions of insulin and other hormones. He received his M.D. degree from the University of Delaware in 1954.