Reverse micelles size characteristics

Reverse micelles from PMAA and PAA-containing copolymers have been extensively studied by Eisenberg and coworkers [104,105]. These authors considered the micellization of the so-called "block ionomers formed of a major PS block linked to ionized PAA and PMAA segments. Stable spherical micelles were formed by these copolymers in organic solvents such as toluene. Their characteristic size was systematically investigated by a combination of experimental techniques including TEM, SAXS, DLS, and SLS. The micelles were shown to consist of an ionic core and a PS corona. The mobility of the PS segments located near the ionic core was found to be restricted, as discussed in Sect. 2.4. 

In order to be exploitable for extraction and purification of proteins/enzymes, RMs should exhibit two characteristic features. First, they should be capable of solubilizing proteins selectively. This protein uptake is referred to as forward extraction. Second, they should be able to release these proteins into aqueous phase so that a quantitative recovery of the purified protein can be obtained, which is referred to as back extraction. A schematic representation of protein solubilization in RMs from aqueous phase is shown in Fig. 2. In a number of recent publications, extraction and purification of proteins (both forward and back extraction) has been demonstrated using various reverse micellar systems [44,46-48]. In Table 2, exclusively various enzymes/proteins that are extracted using RMs as well as the stability and conformational studies of various enzymes in RMs are summarized. The studies revealed that the extraction process is generally controlled by various factors such as concentration and type of surfactant, pH and ionic strength of the aqueous phase, concentration and type of CO-surfactants, salts, charge of the protein, temperature, water content, size and shape of reverse micelles, etc. By manipulating these parameters selective sepa-... 

The addition of macrocycles on CdS synthesis in reverse micelles induces a strong change in absorption spectra. For a given water content, a red shift of absorption onset is observed in presence of macrocycles. This effect is more pronounced in presence of Kryptofix 222 and when the CdS nanocrystallite synthesis is realized in presence of an excess of sulfide S2 ions (x = ). This red shift is characteristic of an increase in the average nanocrystallite size. It can be noticed that absorption of CdS particles synthetized in reverse micelles in presence of an excess of cadmium Cd2+ ions (x = 2) is reduced in presence of macrocycles. This indicates a decrease in the yield of CdS particles and is attributed to complexation of functionalized... 

Reversed micelle-entrapped, colloidal CdS showed the characteristic weak fluorescence emission (Figure 2), previously observed in homogeneous solutions (16-19). However, the maximum emission intensity corresponded to full band gap emission (approximately 500 nm) and was not red-shifted as observed in homogeneous solution (17). This discrepancy might arise from the mode of prep>aration (H S instead of Na S), or from the specific effect of surfactant aggregates. 7 lternatively, tras can be the result of a size... 

The size and characteristics of soft-core reverse micelles are critically dependent upon the water content of the solution. The water present tends to accumulate with the soft-core to form an isolated pool which may exhibit unique properties. At a low ratio of water to surfactant (Wo < 10) the activity of the water is greatly diminished as compared with that of bulk water. The quantity of water... 

To further test pyridine-N-oxide as an indicator, the solvatochromic data are correlated versus micelle radius in Figure 5. The Xmax values for pyridine-N-oxide were determined in solutions of. 025 M AOT in two solvents, n-bctane d n-hexane. For a given Wq the values are very similar in the two solvents. The micelle radii are from the photon correlation experiments of Zulauf and Eicke (, at the same AOT concentration, for a similar solvent, isooctane. It is widely accepted that Wo is a good indicator of the size of reverse micelles, as is evident in the relationship for the two horizontal axes in the figure. There is a relatively linear relationship between micelle size and Xmax for a Wq up to 15. The Xmax this point approaches that of pure water. This is in accord with Eicke and Kvita (28). who indicate that at a Wq of approximately 15, the water pool has the characteristics of free water. These results supply additional evidence of pyridine-N-oxide s hydrophilic nature and utility as an indicator. 

In the following years some more studies appeared in the literature concerning trypsin activity in reverse micelles in relation to various characteristics of the reaction medium. Fadnavis et al. studied the pH dependence of hydrolytic activity of trypsin in CTAB reverse micelles toward a positively charged model ester substrate [74]. It was found that enzyme activity variations as a function of w are pH dependent. In 2005, Dasgupta and coworkers related the catalytic activity of trypsin in reverse micelles formulated with cationic surfactants with the concentration of the water-pool components and the aggregate size to delineate the independent role of both parameters [75]. Finally, in 2006, the influence of ethylene glycol on the thermostability of trypsin in AOT reverse micelles was examined and was found to exhibit a positive effect [76]. 

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