1. a phosphorus-containing substance found in cell nuclei, now known to include nucleic acids
Usage: biochemistry; historical term

Examples

• Early biochemists discovered nuclein in the nuclei of white blood cells.
• The term nuclein was used before scientists understood the structure of DNA.
• Nuclein was first isolated from pus-soaked bandages in 1869.
• Modern scientists recognize that nuclein contains what we now call nucleic acids.
• The discovery of nuclein was an important step in understanding cellular biology.