By the 1940s, another kind of nucleic acid other than DNA was discovered, this one called RNA. Phoebus Levene (1869–1940), a Russian-born chemist, further refined the work of German biochemist Albrecht Kossel (1853–1927), who was awarded the 1910 Nobel Prize for determining the composition of nuclein. At the time of Kossel’s work, it was not clear that DNA and RNA were different substances. In 1909, Levene isolated the carbohydrate portion of nucleic acid from yeast and identified it as the pentose sugar ribose. In 1929, he succeeded in identifying the carbohydrate portion of the nucleic acid by isolating it from the thymus of an animal. It was also a pentose sugar, but it differed from ribose in that it lacked one oxygen atom. Levene called the new substance deoxyribose. Thus, these studies defined the chemical differences between DNA and RNA by their sugar molecules.