Kuhn, << koon, >> Richard (1900-1967), a German chemist, won the 1938 Nobel Prize for chemistry. But the Nazi government forced him to decline it. He did notable vitamin research, especially on the carotenelike substances. He isolated riboflavin (vitamin B-2) from egg albumin. Kuhn was born in Vienna. He became director of the biochemistry section of the Max Planck Institute in 1937.