Any scientist involved in proteomics or protein engineering, will stand by the fact that detergents are indispensable tools for isolation and solubilization of integral membrane proteins and protein complexes from biological membranes. For these studies, it is very important to have intact protein structures in their native biological form in order to evaluate their structure, function, dynamics and binding of ligands.
3 Major Detergent Groups
- Ionic: These detergents are either anionic or cationic. They are very efficient at stabilizing proteins, but almost always cause denaturation of the protein to some extent. An example of an ionic detergent is Sodium Dodecyl Sulfate (SDS).
- Non-Ionic: They have an uncharged hydrophilic head and are either polyethylene or glycoside surfactants. These relatively mild detergents, efficiently solubilize proteins intact in their functional state. Examples of Non-Ionic Detergents are, n-Dodecyl-β-D-maltopyranoside (DDM), and n-Octyl-β-D-Glucopyranoside (OG).
- Zwitterionic:These detergents have a neutral charge, hence possess both ionic and non-ionic properties. Zwitterionic detergents effectively solubilize proteins and successfully maintain the native state and charge of individual proteins.Â Examples of zwitterionic detergents are CHAPS, CHAPSO
A closer look at DDM
Also known as DDM, N-Dodecyl-β-D-maltopyranoside is a non-ionic detergent and a glycoside based surfactant. In 1980, Ferguson-Miller et al at Michigan State University developed n-Dodecyl-β-D-maltopyranoside (DDM) as part of a successful effort to purify an active, stable, monodisperse form of cytochrome c oxidase.
- Structurally, DDM has a bulky head containing two sugar rings and a non-charged alkyl glycoside chain.
- It is a relatively mild detergent that solubilizes protein by disrupting the lipid-lipid interaction or the lipid-protein interactions. DDM successfully solubilizes integrated membrane proteins in their native state and or protein complexes.
- The critical micelle concentration (CMC) of n-dodecyl-β-d-maltopyranoside is approximately 0.18 mM in water and decreases in the presence of sodium chloride or sucrose and increases in urea.
- Due to its low CMC, DDM is not easily removed by dialysis. Typically detergents with low CMC are removed by adsorption to hydrophobic beads.
- DDM has been used to solubilize the multidrug-transporter protein, EmrE, as well as the nucleoside-specific porin protein, Tsx.
- Seddon, Annela M., et al. “Membrane Proteins, Lipids and Detergents: Not Just a Soap Opera.” Biochimica Et Biophysica Acta (BBA) – Biomembranes, vol. 1666, no. 1-2, 3 Nov. 2004, pp. 105–117., doi:10.1016/j.bbamem.2004.04.011.
- Pagliano, Cristina, et al. “Comparison of the α and β Isomeric Forms of the Detergent n-Dodecyl-D-Maltoside for Solubilizing Photosynthetic Complexes from Pea Thylakoid Membranes.” Biochimica Et Biophysica Acta (BBA) – Bioenergetics, vol. 1817, no. 8, Aug. 2012, pp. 1506–1515., doi:10.1016/j.bbabio.2011.11.001.
- Churchward, Matthew A., et al. “Enhanced Detergent Extraction for Analysis of Membrane Proteomes by Two-Dimensional Gel Electrophoresis.” Proteome Science, vol. 3, no. 5, 7 June 2005.