The discovery of DNA, circa 1869

Miescher's laboratory located in an old Tübingen castle kitchen.

Courtesy of Tübingen University Library

In the winter of 1869, the young Swiss doctor, Friedrich Miescher, was attempting nothing less than to uncover the biochemical nature of life using leukocytes he isolated from the pus on surgical bandages. His laboratory was located in the kitchen of a medieval castle owned by the University of Tübingen in Germany.

The photograph shows a large distillation apparatus in the far corner of the room which produced distilled water and several smaller utensils, such as glass alembics and a glass distillation column on the side board. The adjacent laboratory of his mentor, the renowned biochemist, Felix Hoppe-Seyler, was more amply equipped.

As part of his protocol, Miescher rinsed the pus-soaked bandages with a dilute solution of sodium sulphate to wash out the white blood cells, then washed the samples with warm alcohol and ether to extract the lipids and other lipophilic molecules. He also digested the cells with solutions of the protease pepsin, which Miescher obtained by rinsing pig stomachs, to break down the proteins. This left him with a powdery sediment. When he added sodium carbonate, an alkaline solution, the sediment dissolved; when he then added acid, he obtained a precipitate again (Human Genet, 122:565-81, 2008).

Felix Hoppe-Seyler's laboratory.

Courtesy of Tübingen University Library

He was puzzled. The substance could not be dissolved in organic solvents, and thus was not a lipid. But it also did not behave like a protein, because the protease solution didn't break it down. He performed elementary analyses to determine its composition; besides the expected carbon, oxygen, hydrogen and nitrogen, he also found phosphorous in quantities unheard of at the time. Miescher was electrified by his findings. He realized that he had discovered a new type of molecule. Due to its presence in the cells' nuclei (he separated the nuclei from the rest of the cells during his protocol), Miescher named the mysterious substance nuclein.

More than a year later, Hoppe-Seyler confirmed the results and included them in an issue of the Medicinisch-chemische Untersuchungen, a leading journal published by Hoppe-Seyler himself. In 1871, the scientific world first learned about the existence of DNA.

Correction: When originally posted, the reference contained an incorrect year of publication. The Scientist regrets the error, which has been corrected.