Friedrich Miescher

Friedrich Miescher isolates the nuclear substance he named nuclein

His raw material arrived as pus-coated surgical dressings from the university's surgical clinic.

Winter 1868–69, in Hoppe-Seyler's laboratory

Friedrich Miescher spent the winter of 1868–69 in Felix Hoppe-Seyler's laboratory at the University of Tübingen, analysing leukocytes washed from pus-covered surgical bandages supplied by the university's surgical clinic.

He separated intact cells with roughly 1.5% sodium sulfate — with no centrifuge, waiting for the leukocytes to settle — then removed cellular material and proteins, extracted the nuclei under alkaline conditions and precipitated a substance by adding acid. A letter of 26 February 1869 to his uncle Wilhelm His is the earliest surviving description of the result.

A precipitate that refused to behave like protein

The precipitate was unusually rich in phosphorus and chemically unlike any known protein. Because it came from nuclei, Miescher called it “nuclein”; a surviving preparation measures 2.56 ± 0.06% phosphorus by mass.

In that letter Miescher concluded that the material belonged to no known class of protein. No exact day of successful isolation is recorded; the letter is simply the earliest surviving account of it.

What he had not shown

Miescher did not establish that nuclein was hereditary material, and he described nothing about DNA's structure; the double-helix model came in 1953. Historians also caution that his first material was an impure nucleic-acid preparation, not chemically pure DNA.

There was no immediate public scientific response because the result remained unpublished. Hoppe-Seyler and other researchers repeated the work before the paper appeared in 1871.

Sources

Researched 23 Aug 2026 6 sources 2 audit passes

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What the sources leave uncertain

The year 1869 is well supported, but no exact experimental day is known. The work began in winter 1868–69; February 26 is the date of the earliest surviving letter describing the finding, not necessarily the date of the successful isolation.
Historians differ over how to translate “nuclein” into modern terms. Miescher’s first material was an impure nucleic-acid preparation or DNA associated with proteins, not a modern preparation of chemically pure DNA.