Apparent critical micellar concentration

Chemical relaxation methods [52] show evidence of a distribution of relaxation frequencies rather than a single one as found with classic ion detergents [193]. Thus, in agreement with the above conclusions, NaC and NaDC apparently self-associate over a whole range of concentrations and not at some critical micellar concentration. Further, the relaxation frequencies are strongly concentration dependent, suggesting that the distribution of aggregate sizes is wide and shifts upwards as bile salt concentration is increased [52]. 

Fig. 6 Typical micellar equilibration time, Tnuc, as a function of the unimer concentration normalized by the equilibrium value (cmc). Dotted horizontal line corresponds to a time of 1 h and defines the apparent critical micelle concentration, cmcapp. Reproduced fi om [68]...

Reversed-Phase Liquid Chromatography (RPLC) is an important tool in protein chemistry. Examination of sorption isotherms revealed that alcohohc buffers did not desorb proteins near physiological pH in RPLC systems, while buffers containing a poly(ethoxy alcohol) surfactant did not desorb protein at pH 2, but they did at pH 7 with concentrations of surfactant apparently well above the critical micellar concentration (cmc) [2]. It has been proposed that a necessary condition for the desorption of a protein from a surface is that the surface tension of the solvent falls between that of the protein and the surface [6]. This condition is fiilfilled for many proteins with surfactant solutions near conditions of physiological pH and ionic strength. Therefore, it was expected that separations of proteins could be thieved in these conditions. 

Very large solvent effects arc also observed for systems where the monomers can aggregate either with themselves or another species. For example, the apparent kp for polymerizable surfactants, such as certain vinyl pyridinium salts and alkyl salts of dimethylaminoalkyl methacrylates, in aqueous solution above the critical micelle concentration (cmc) are dramatically higher than they are below the cmc in water or in non-aqueous media.77 This docs not mean that the value for the kp is higher. The heterogeneity of the medium needs to be considered. In the micellar system, the effective concentration of double bonds in the vicinity of the... 

Note that complete baseline resolution has Rg > 1.5, and this level can be achieved for each analyte with at least one selector. In general, the best results are observed with ristocetin A, and teicoplanin is the most distinct of the three. This last antibiotic has particular aggregation properties. It is surface active due to the presence of a long hydrophobic chain in the radical R in the acyl group of jS-o-glucosamine (see above) and forms micellar aggregates above the critical micelle concentration of O.lSmM. Apparently, this may affect its recognition properties. 

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