nuclein

Nuclein is the historical name for the substance later known as nucleic acids. It was first described in 1869 by Friedrich Miescher, who, while studying the chemistry of white blood cells, isolated an acidic, phosphorus-containing substance from the cell nuclei and named it nuclein. He observed that it differed from proteins and that it resided in the cell nucleus.

During the late 19th and early 20th centuries, researchers established that nuclein was the genetic material of cells, and the term nucleic acid emerged to describe its true nature as a polymer of nucleotides. The two main classes identified were deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

With advances in molecular biology, nucleic acids were shown to carry genetic information and to be capable of replication and expression. The structure of DNA as a double helix was elucidated in 1953 by Watson and Crick, with later refinements by Franklin and Wilkins; the roles of RNA in transcription and translation followed. The term nuclein gradually fell out of use in favor of nucleic acid or DNA/RNA as specific descriptors.

Today, the word nuclein remains of historical interest, used mainly in literature on the history of genetics. It is recognized as the earliest term for the family of molecules that include DNA and RNA, essential to heredity and cellular function.