Solubilization in reversed micelles

It is also possible to solubilize finite amounts of solid substances within reversed micelles [38 0], For example, in Figure 2, the UV-vis spectrum of CoCNOs) solubilized in reversed micelles of C12E4 is compared with that of a thin film of bulk Co(N03)2. It is interesting to note both similarities and differences between the two spectra. Another example is given by urea, which, as emphasized by the IR spectrum reported in Figure 3, can be... 

The aqueous cores of reverse micelles are of particular interest because of their analogy with the water pockets in bioaggregates and the active sites of enzymes. Moreover, enzymes solubilized in reverse micelles can exhibit an enhanced catalytic efficiency. Figure B4.3.1 shows a reverse micelle of bis(2-ethylhexyl)sulfosuccinate (AOT) in heptane with three naphthalenic fluorescent probes whose excited-state pK values are much lower than the ground-state pK (see Table 4.4) 2-naphthol (NOH), sodium 2-naphthol sulfonate (NSOH), potassium 2-naphthol-6,8-disulfonate (NSOH). The spectra and the rate constants for deprotonation and back-recombination (determined by time-resolved experiments) provide information on the location of the probes and the corresponding ability of their microenvironment to accept a proton , (i) NDSOH is located around the center of the water pool, and at water contents w = [H20]/[A0T] >... 

Fig. 3a-c. Various methods of protein solubilization in reverse micelles. (Reproduced from [145] with permission of Wiley)... 

Nucleic acids can also be solubilized in reverse micelles, including ribosomes and plasmids, (Imre and Luisi, 1982 Palazzo and Luisi, 1992 Pietrini and Luisi, 2002 2004 Ousfuri et al, 2005), which also gives rise to a series of interesting structural and thermodynamic questions. In particular, high-molecular-weight... 

Nguyen, H.T., Clathrate Hydrate Formation and Protein Solubilization in Reversed Micelles, Ph.D. Thesis, Tulane University, LA (1991). 

Evans, R. M., and S. J. Farr. 1993. Aerosol formulations including proteins and peptides solubilized in reverse micelles and process for making the aerosol formulations. US Patent 5,230,884. 

Goklen, K. E., and Hatton, T. A. (1987). Liquid-liquid extraction of low molecular-weight proteins by selective solubilization in reversed micelles. Sep. Sci. Technol. 22, 831-841. 

The basic pH brings about an electrostatic repulsion between the protein surface and anionic surfactants. On the other hand, the high salt concentration avoids the electrostatic adsorption of the surfactants. Both factors modify the electrostatic interaction between the proteins solubilized in reverse micelles and the surfactant layer. Indeed, however, in the back extraction process, the proteins solubilized in the droplets cannot suffer such a modification because of the little degree of coalescence of the reverse micelles containing proteins with a bulk aqueous solution or vacant reverse micelles. This is one of the reasons why the back extraction process is much slower than the forward extraction process. 

Zhang H, Lu J, Han B. Precipitation of lysoz5me solubilized in reverse micelles by dissolved CO2. J Supercrit Fluid 2001 20 65-71. 

FIG. 3 a-Chymotrypsin solubility (protein concentration) in reverse micelles of 0.1 M AOT in octane, as a dependence on the degree of surfactant hydration (water-to-AOT molar ratio), for protein molecules with chemically modified surface groups. ( ) Acetyl-a -ch5miotrypsin (O) succinyl-a-chymotrypsin (—) maximal concentration of nonmodified native a -ch5miotrypsin solubilized in reverse micelles. 

FACTORS AFFECTING WATER SOLUBILIZATION IN REVERSE MICELLES... 

In Section 3.3 we have briefly indicated that there are various factors that can affect water solubilization in reverse micelles. The importance of the oil-water interface in the context of water solubilization cannot just be overemphasized, and the entity that first comes to the forefront is the surfactant film that separates the two immiscible phases. At the very beginning, therefore, some basic and relevant points on the surfactant film are described below in brief [113, 114, 124, 125, 3]. The interfacial surfactant film can be described as a two-dimensional system in which one can consider a pressure term n [113] this term, characteristic of the film, defines the difference in the oil/water interfacial tension before and after addition of the surfactant to form an interfacial film ... 

The iron salts were first dissolved in 0.05 mol/1 H2SO4 before solubilization in reverse micelles, so as to avoid uncontrolled precipitation of Fe203. 

Figure 4 Reverse micelles in organic phase. (Adapted from Nitsch W and Plucinski P (1990) Two-phase kinetics of the solubilization in reverse micelles. Journal of Colloid and Interface Science 136 338-351.)...

Au CO2 HAuCU N-EtFOSA For PEC-400/N-EtF0SA/C02 system, (the molar ratio of PEC solubilized in reverse micelles to surfactant) 0.36 For PEC-1 000/N-EtF0SA/C02 system, lV h0.28 Not mentioned in the paper, from TEM image 5 nm [50]... 

Horse liver alcohol dehydrogenase (HLADH) is an enzyme known to stereo-selectively oxidize and reduce a wide range of alcohol and ketone substrates. In a study that appeared in 1987, HLADH was solubilized in reverse micelles formed with AOT/cyclohexane and the oxidation of ethanol and reduction of cyclohexanone in a coupled substrate/coenzyme recycling system was investigated [147]. Activity and stability studies showed that the enzyme remains active and stable for at least 2 weeks while the charged coenzyme is retained within the dispersed water droplets. 

Walde, P., Han, D., Luisi, P.L. 1993. Spectroscopic and kinetic studies of lipase solubilized in reverse micelles. Biochemistry 32,4029-4034. 

J. Sunamoto and T. Hamada, Solvatochromism and Thermochromism of Co(II) complexes solubilized in reversible micelles. Bull. Chem. 

Figure 10.19. Solid surface drying by water solubilization in reversed micelles (a) wet metal surface (b) drying surfactant micelles begin to absorb water (c) dry surface and solubilized waters.

Lipase solubilized in reverse micelles or w/o microemulsions was found to catalyze the interesterification reaction. This process was found to be very effective, and it was possible to substitute any fatty acid group in any selected position on glycerol [57,58]. Interesterification of liquid oils with a highly saturated fat yields fats with little or no trans isomers and high levels... 

Chen and Hong [65] showed that butterlike or cheeselike flavors could be obtained by the hydrolysis of butter fat by Candida cylidracea lipase solubilized in reverse micelles of soybean lecithin in a continuous butter oil phase. The enzyme exhibited less sensitivity to pH and temperature compared with an emulsified system and its activity increased with increasing surfactant or enzyme concentration. Due to a large interfacial area, a much higher enzyme concentration could be used before the system reached saturation. 

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