Ionic detergents, sodium dodecyl sulfate

Tailing peaks or longer than expected elution volumes are sometimes caused by low solubility of the protein in the mobile phase. Using a trial-and-error process, select the proper pFf and ionic strength to address this problem. Detergents such as sodium dodecyl sulfate (SDS) are sometimes helpful but, because they change the conformation of many proteins and are difficult to remove from the column should be used only if other methods fail. 

Detergents have been developed to avoid this problem of soap in hard water. Their structures are similar to (although more varied than) that of soap, but they are less likely to form insoluble compounds with hard water ions. Some detergents are ionic like soap, and some are molecular. For example, in sodium dodecyl sulfate (SDS), a typical ionic detergent, the -C02 portion of the conventional soap structure is replaced by an -0S03 group, which is less likely to link with hard water cations and precipitate from the solution ... 

SDS, sodium dodecyl sulfate 2-ME. 2-mercaptoethanol CHES, cyclo-hexylamine sulfonic acid NP-40, Non-ident 40 non-ionic detergent PMSF, phenylmethylsulfonyl fluoride CHAPS, 3-t(3-cholam1dopropyl) dImethvlammonloH -propane sulfonate. ... 

Ionic detergents, such as cetyltrimethylammonium bromide or sodium dodecyl sulfate, give pore sizes between 2 and 4 nm, whereas nonionic surfactants such as the Pluronics and the Tween surfactant series (ethoxylated sorbitan esters) give materials with larger pores (around 10 nm) and thicker walls (Table 18.1). 

This deviation may affect the separation potential In preparative SEC and It Is of primary concern when SEC Is used to determine protein siolecular weights. Strong protein denaturants, eg., Ionic detergents such as sodium dodecyl sulfate and chaotroplc salts such as guanidine hydrochloride, are known to convert native proteins to random coll conformations (28). Fish et al. (29) first reported that the use of denaturants to Induce uniform protein conformation greatly enhanced the resolution potential and accuracy of protein molecular weight calculations In conventional SEC. 

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