Friedrich Miescher purifies nuclein

Background. Johannes Friedrich Miescher, a Swiss physician and biologist, conducted research in Felix Hoppe-Seyler's laboratory at the University of Tübingen. In 1869, he isolated various phosphate-rich chemicals from the nuclei of white blood cells, naming them nuclein. This discovery paved the way for the later identification of DNA as the carrier of inheritance.

Methodology. Miescher devised specific salt solutions, including sodium sulfate, to filter cells. Without centrifuges, he allowed cells to settle in beakers to isolate nuclei from cytoplasm. He subjected these purified nuclei to alkaline extraction followed by acidification, resulting in a precipitate called nuclein, which contained phosphorus and nitrogen but not sulfur.

Verification. Hoppe-Seyler repeated all of Miescher's research himself before publishing it in his journal. This verification occurred because one of his earlier students had made false claims. The significance of the discovery was not immediately apparent, leading to initial inquiries into its chemical structure by Albrecht Kossel.