Nucleins

Nucleins is a historical term used to describe the substance isolated from cell nuclei that contains nucleic acids bound to proteins. In contemporary biology, the expression is largely superseded by descriptions such as nucleic acids, nucleoproteins, or chromatin, depending on context. The concept nonetheless played a foundational role in the development of molecular biology.

The term originated with the work of Friedrich Miescher in 1869, who extracted a substance from the nuclei of white blood cells in pus and named it nuclein. He noted that it contained phosphorus and behaved as an acid. Over time, the component was linked to nucleic acids, and the name nuclein fell out of common use as scientists distinguished nucleic acids from associated proteins.

Nucleins, in the historical sense, referred to complexes of nucleic acids with proteins. In modern terms, these are described as nucleoproteins. In eukaryotes, DNA is organized with histone and non-histone proteins into chromatin, forming structures such as nucleosomes. In prokaryotes, DNA is associated with basic proteins to form a less organized nucleoid region. Viruses also contain nucleoprotein complexes, where nucleic acids are packaged with proteins for replication and protection.

Functionally, nucleoproteins are essential for genetic information storage, replication, transcription, and regulation. They participate in chromatin remodeling, RNA processing, and the assembly of ribonucleoprotein particles. The historical term nuclein remains of interest primarily for historical context, while modern terminology emphasizes nucleic acids, nucleoproteins, and chromatin.