Friedrich Miescher

Johannes Friedrich Miescher
Friedrich Miescher
Born	(1844-08-13)13 August 1844 Basel
Died	26 August 1895(1895-08-26) (aged 51) Davos
Nationality	Swiss
Fields	Biology
Known for	Discovery of nucleic acids

Johannes Friedrich Miescher (13 August 1844 – 26 August 1895) was a Swiss physician and biologist. He was the first researcher to isolate and identify nucleic acid.

Miescher isolated various phosphate-rich chemicals, which he called nuclein (now nucleic acids), from the nuclei of white blood cells in 1869 in Felix Hoppe-Seyler's laboratory at the University of Tübingen, Germany, paving the way for the identification of DNA as the carrier of inheritance. The significance of the discovery, first published in 1871, was not at first apparent, and it was Albrecht Kossel who made the initial inquiries into its chemical structure. Later, Friedrich Miescher raised the idea that the nucleic acids could be involved in heredity.

Miescher came from a scientific family: his father and his uncle held the chair of anatomy at the University of Basel. As a boy he was shy but intelligent. He had an interest in music, and his father performed publicly. Miescher studied medicine at Basel. In the summer of 1865 Friedrich worked for the organic chemist Adolf Stecker in Göttingen, but his studies were interrupted for the year when he became ill with typhoid fever, which left him hearing-impaired. However, he still received his MD in 1868.

Miescher felt that his partial deafness would be a disadvantage as a doctor, so he turned to physiological chemistry. He originally wanted to study lymphocytes but was encouraged by Felix Hoppe-Seyler to study neutrophils. He was interested in studying the chemistry of the nucleus. Lymphocytes were difficult to obtain in sufficient numbers to study, while neutrophiles were known to be one of the main and first components in pus and could be obtained from bandages at the nearby hospital. The problem was, however, washing the cells off the bandages without damaging them.

Miescher devised different salt solutions, eventually producing one with sodium sulfate. The cells were filtered. Since centrifuges were not available at the time, the cells were allowed to settle to the bottom of a beaker. He then tried to isolate the nuclei free of cytoplasm. He subjected the purified nuclei to an alkaline extraction followed by acidification, resulting in the formation of a precipitate that Miescher called nuclein (now known as DNA). He found that this contained phosphorus and nitrogen, but not sulfur. The discovery was so unlike anything else at the time that Hoppe-Seyler repeated all Miescher's research himself before publishing it in his journal. Miescher then went on to study physiology at Leipzig in the laboratory of Carl Ludwig for a year before being appointed professor of physiology.