Nonidet, also known as NP-40 (Nonidet P-40), is a widely used nonionic detergent in biochemistry and molecular biology. It belongs to the class of nonionic detergents, characterized by their mild nature and ability to solubilize membrane proteins without denaturation. NP-40 is composed of a hydrophilic polyethylene oxide chain and a lipophilic alkylphenyl group, providing it with both hydrophilic and hydrophobic properties. Commonly employed in protein extraction and cell lysis procedures, NP-40 effectively disrupts cell membranes, facilitating the release of cellular components. Its mild detergent properties make it suitable for maintaining the native structure and function of proteins during solubilization, crucial for downstream applications such as immunoprecipitation and enzyme assays.