Tween 20

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Tween 20 is a transparent viscous liquid that is commonly used in Molecular Biology as a potent nonionic detergent, emulsifier and as a blocking agent in immunoassays, such as Western Blotting [1]. Other uses of Tween 20 include expulsion of membrane peripheral proteins and lysis of mammalian cells[1].

Particularly is Western Blotting, Tween 20 is used to decrease the possibility of unspecific binding of proteins (such as immunoassays) onto the nitrocellulose/nylon blotting membrane[2]. This improves visualisation of the protein of interest by reducing the background noise (binding of primary and/or secodary antibody to the membrane)[2].

Other potent blocking agents include nonfat dry milk, bovine serum albumin, casein and possibly nonfat soymilk[2]


  1. 1.0 1.1 Sigma-Aldrich (n.d). Tween 20. Available at: [Last accessed 20/11/13].
  2. 2.0 2.1 2.2 Galva, C., Gatto, C., Milanick, M. (2012). Soymilk: An effective and inexpensive blocking agent for immunoblotting. Available at: [Last accessed 20/11/13].

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