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Non-ionic Detergents

Introduction

Non-ionic detergents contain uncharged hydrophilic glucose-derived or polyoxyethylene head groups. This type of detergent is considered to be mild as the destabilization they cause is almost completely reversible. This capacity is explained by the fact that non-ionic detergents typically disrupt protein-lipid (and lipid-lipid) but not protein-protein interactions, thus maintaining (or better to phrase—not interfering with) the native state of a protein. Based on this, the primary application of non-ionic detergents is in the study of various biologically active forms of membrane proteins. However, the degree of destabilization correlates well with the length of the acyl chain of the detergent. In this regard, short (C7–C10) hydrocarbon chains (e.g., octylglucoside and nonylmaltoside) can often lead to deactivation of the protein, in contrast to their corresponding intermediate (C12–C14) chain-length derivatives (e.g., dodecylmaltoside) [1].

The non-ionic detergents micelle.Fig. 1. The non-ionic detergents micelle.

Classification

Non-ionic detergents can be further classified into two types: polyoxyethylene (and related detergents), and glycosidic detergents.

  • Detergents based on polyoxyethylene and similar compounds contain a neutral, polar head group and the tails are composed of hydrophobic oxyethylene chains, or, in some cases, ethylene glycoether chains. The type of detergent includes Triton family (Triton X-100, Triton X-114, Nonidet P-40, etc.) and Tween family (Tween-20, Tween-40, Tween-60, Tween-80, etc.). All members of the Triton family are quite similar, differing slightly in their average number (n) of monomers per micelle (9.6, 8.0, and 9.0, respectively) and the size distribution of their polyethylene glycol (PEG)-based headgroup. Tween family is polysorbate surfactants with a fatty acid ester moiety and a long polyoxyethylene chain and they have very low critical micelle concentration (CMC).

Structure of Triton X-100.Fig. 2. Structure of Triton X-100.

  • Detergents with a glycosidic base tend to use a sugar as the head group, such as glucose or maltose, and contain an alkyl polymer tail. The typical detergents in these types are maltoside family (such as n-dodecyl-β-D-maltoside, beta-decyl-maltoside, etc.). Maltosides are composed of a hydrophilic maltose and a hydrophobic alkyl chain. Variation in the alkyl chain confers a range of detergent properties including CMC and solubility.

 Structure of n-dodecyl-β-D-maltoside.Fig. 3. Structure of n-dodecyl-β-D-maltoside.

Applications

Due to the mild and nondenaturing characteristics of non-ionic detergents, they are frequently used in studies of membrane proteins when compared to other applications. It is reported that a majority of the detergents used in the purification and structural determination of membrane proteins are non-ionic detergents. According to the report from Stetsenko et al., the non-ionic detergents account for a large part of the top 10 detergents used for the structural analysis of membrane proteins [2]. They are n-dodecyl-β-D-maltopyranoside (DDM), n-decyl-β-D-maltopyranoside (DM), n-octyl-β-D-glucopyranoside (OG), n-nonyl β-D-glucopyranoside (NG), polyoxyethylene 8 dodecyl ether (C12E8), n-undecyl-β-D-maltopyranoside (UM or UDM), lauryl maltose neopentyl glycol (LMNG or MNG-3), Triton X-100 and digitonin, respectively. And DDM, DM, and OG dominate, both for purification and crystallization. Looking at the results, one can confidently say that the non-ionic detergents rule the field of structural studies on membrane proteins. In addition, according to the result of statistics analysis, DDM and DM are reported as the detergents of choice for more than a half of structural studies on membrane proteins. With an addition of UDM, Cymal-5, Cymal-6, OG and NG, the total fraction of sugar-based detergents is around 75% of structural studies on membrane proteins.

The bar representation (in %) of different detergents used for (A) membrane proteins purification and (B) crystallization (up to 31 December 2016).Fig. 4. The bar representation (in %) of different detergents used for (A) membrane proteins purification and (B) crystallization (up to 31 December 2016).

What Can We Do?

Alfa Chemistry utilizes many years of academic know-how to develop high purity and high-quality detergents for clients from both research and industry in many regions worldwide. Now, we have independently developed and produced a variety of non-ionic detergents for membrane proteins research. We assure that our products are the most wanted. You can click on our product list for a detailed view. If you do not find the product you want, we also provide you with custom synthesis service. For any of your requirements, we guarantee to provide you with cutting-edge solutions and products and efficient services.

References

  1. Errasti-Murugarren E., et al. Membrane protein stabilization strategies for structural and functional studies[J]. Membranes, 2021, 11(2): 155.
  2. Stetsenko A. and Guskov A. An overview of the top ten detergents used for membrane protein crystallization[J]. Crystals, 2017, 7(7): 197.

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