Kossel, Albrecht (älˈbrĕkht kôsˈəl) [key], 1853–1927, German physiologist. He was professor at Heidelberg from 1901. He specialized in the physiological chemistry of the cell and its nucleus and of proteins, including nucleins. He discovered the purine adenine and the pyrimidine thymine. For this work he received the 1910 Nobel Prize in Physiology or Medicine. He wrote Protamines and Histones (tr. 1928).