Detergents ionic/nonionic

Detergents. Under appropriate conditions of pH, ionic strength and temperature, detergents (ionic sodium lauiyl sulphate, sodium deoxycholate, sodium cholate and cetyldiethyl-ammonium bromide, or nonionic Tweens and Tritons), can be used to lyse cells. Detergents may however cause enzyme inactivation and may need to be removed before purification. 

Detergents help dissolve cellular membranes. All detergents are polar lipids that are water soluble with a hydrophilic (polar) ends and can bind the hydrophobic (apolar) ends in the center of the lipid bilayer (Fig. 5.4a). The groups that make up the hydrophilic portion determine the type of detergent. There are two types of detergents, ionic and nonionic (Fig. 5.5). 

Based on the similarities in their behavior and characteristics of various types of detergents, it is essential that they are classified, and different types of detergents are categorized based on certain commonalities. Based on the nature of the hydrophilic head group, they can be broadly classified as ionic, nonionic, and zwitterionic detergents. Some of the examples of these surfactants are given in Table 26.1. 

Chem. Descrip. Formulated detergent Ionic Nature Anionic/nonionic Uses Detergent, wetting agent in textiles Properties Liq. cloud pt. > 100 C (1% aq.) 90% act. 

Chem. Desaip. Blended liq. detergent with nonionic foam stabilizer Ionic Nature Anionic/nonionic Uses Detergent Properties Liq. 36% cone. 

Chem. Descrip. Complex blend of phosphated alcohols and nonionic detergents Ionic Nature Nonionic/anionic... 

In acidic media, amine oxides and anionic surfactants form precipitates the CMC is much greater than in neutral or alkaline media. Change in CMC parallels change from ionic to nonionic form. Amine oxides are stable in formulated detergent products and do not act as oxidizing agents. Composition and function of representative commercial amine oxides are given in Table 26. 

Protease performance is strongly influenced by detergent pH and ionic strength. Surfactants influence both protease performance and stabiUty in the wash solution. In general, anionic surfactants are more aggressive than amphoteric surfactants, which again are more aggressive than nonionic surfactants. 

Stable liquid detergents are obtained by polyacetalcarboxylate builders, ionic or nonionic surfactants, and common ingredients of detergents. If esters of phosphoric acid are used as anionic surfactants a detergent of this kind with 62% of water retained a single phase after a 30-day storage [213]. 

Nonionic surfactants contain (Fig. 23) no ionic functionalities, as their name implies, and include ethylene oxide adducts (EOA) of alkylphenols and fatty alcohols. Production of detergent chain-length fatty alcohols from both natural and petrochemical precursors has now increased with the usage of alkylphenol ethoxylates (APEO) for some applications. This is environmentally less acceptable because of the slower rate of biodegradation and concern regarding the toxicity of phenolic residues [342]. 

Nonionic surfactants, as mentioned previously, have been widely adopted due to their characteristics and properties and, in particular, because they do not require the presence of undesirable phosphate or caustic builders in detergent formulation. However, the relatively lesser degree of biodegradability is an important disadvantage of the nonionic surfactants compared to the ionic ones. Adsorption on activated carbon and various types of clay particles is, therefore, one of the processes that has been effective in removing heterodisperse nonionic... 

CMC will change if the additive has an effect on the monomer-micelle equilibrium, and also if the additive changes detergent solubility. The CMC of all ionic surfactants will decrease if coions are added. However, nonionic surfactants show very little change in CMC on the addition of salts, which is to be expected from theoretical considerations. The change of CMC with NaCl for SDS is as follows (Figure 3.10) ... 

The SDS-containing solution is supplemented with an excess of a nonionic detergent, e.g., Triton X-100. The electrode buffer is a buffer with low ionic strength, without SDS, and pH nearby the pi of the protein of interest. During electroelution SDS migrates to the anode. 

The bile salts have a peculiar molecular structure compared with ordinary detergents, possessing both an ionic polar group and nonionic hydrophilic hydroxyl groups. These molecules might, therefore, have characteristics related to both anionic and nonionic detergents. 

Several of the synthetic detergents used for dissolving membranes and solubilizing integral membrane proteins. Triton X-100 and octylglucoside are nonionic detergents cetyltrimethylammonium bromide and sodium dodecylsulfate (SDS) are ionic. SDS is also an effective denaturant of proteins and is used in polyacrylamide-gel electrophoresis (see chapter 6). 

A. Ray and G. Nemethy, Effects of ionic protein denaturants on micelle formation by nonionic detergents, J. Am. Chem. Soc. 93... 

As in aqueous detergent solutions it has become customary to distinguish nonionic and ionic surfactants, thereby subdividing the latter into cationic and anionic surfactants. Some authors also include amphoteric surfactants in this group. Typical representatives of these surfactant types are given in Table 1. The distinction between... 

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