Ochoa seated at table in laboratory taking notes and smoking cigarette. No date given. Severo Ochoa de Albornoz (1905-1993) was a Spanish-American physician and biochemist. His interest in biology was stimulated by the publications of the Spanish neurologist and Nobel laureate Santiago Ram籀n y Cajal. Ochoa and Jos矇 Valdecasas isolated creatinine from urine and developed a method to measure small levels of muscle creatinine. In 1930 Ochoa completed and defended the research for his MD thesis. In 1942 he was appointed Research Associate in Medicine at the New York University School of Medicine and subsequently became Assistant Professor of Biochemistry (1945), Professor of Pharmacology (1946), Professor of Biochemistry (1954), and Chairman of the Department of Biochemistry. In 1956, he became an American citizen. In 1959, Ochoa was awarded the Nobel Prize for Physiology or Medicine for his work on the synthesis of RNA. Ochoa continued research on protein synthesis and replication of RNA viruses until 1985. He died in 1993 at the age of 88.