German biochemist who was awarded the Nobel Prize for Physiology or Medicine in 1910 for his contributions to understanding the chemistry of nucleic acids (nucleic acid) and proteins. He discovered the nucleic acids that are the bases in the DNA molecule, the genetic substance of the cell.

After graduating in medicine (1878) from the German University (now the University of Strasbourg), Kossel did research there and at the Physiological Institute in Berlin. In 1895 he became professor of physiology and director of the Physiological Institute at Marburg, going in 1901 to a similar post at Heidelberg, where he eventually became director of the Heidelberg Institute for Protein Investigation.

In 1879 Kossel began studying the recently isolated substances known as “nucleins” (nucleoproteins), which he showed to consist of a protein portion and a nonprotein portion (nucleic acid). From 1885 to 1901 he and his students used hydrolysis and other techniques to chemically analyze the nucleic acids, thus discovering their component compounds: adenine, cytosine, guanine, thymine, and uracil. Kossel also discovered the amino acid histidine (1896), thymic acid, and agmatine.