A broad term, the discussion of detergents on this page will be limited to their use for protein solubilization and purification. A primary source for the following is Dirk Linke’s paper published in Methods in Enzymology, which can be found here.

Detergent Primer

While a typical laundry detergent would contain surfactants, EDTA, enzymes, and a host of other chemicals, the detergents used during membrane protein purification are primarily surfactants. Surfactants are amphiphilic (containing hydrophilic and hydrophobic portions) molecules which when added to a liquid, decrease the surface tension between two liquids.

The picture in the cover is n-dodecyl-beta-D-maltoside, also known as DDM (ligand LMT). This is a common detergent used in membrane protein purification.

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DDM contains two cyclic, hydrophilic headgroups and a long alkane chain. Many detergents you will use during membrane protein purification will resemble this, but not all. The following is digitonin (ligand AJP), a steroidal glycoside purified from Digititalis. A uniquely expensive detergent that burns a bit when exposed to bare skin, digitonin excels at plasma membrane solubilization and interacts directly with cholesterol.

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How can we group and characterize detergents? There are in fact, many ways to do this. We can first try based on the structure and properties of their headgroups.

  1. Nonionic: Nonionic detergents have a hydrophilic headgroup that lacks a charge. Examples include DDM and Triton X-100.
  2. Anionic: Negatively charged, hydrophilic head. SDS, sarkosyl, and sodium cholate are examples of anionic detergents.
  3. Cationic: Cationic detergents have positively charged, hydrophilic heads. Dodecyltrimethylammonium bromide (DTAB) is an example.
  4. Zwitterionic: Both positive and negatively charged groups are found in the head of these detergents. CHAPS is an example of this.