Water-miscible organic solvent, effect

Vazquez-Duhalt, R. Semple, K. M. Westlake, D. W. S., and Fedorak, P. M., Effect of Water-Miscible Organic-Solvents on the Catalytic Activity of Cytochrome-C. Enzyme and Microbial Technology, 1993. 15(11) pp. 936-943. 

Several methods for effective solubilization of drugs into polymer micelles have been developed (Fig. 2). The dialysis method (Fig. 2A) is most widely used for many polymeric micelle systems. The first step involves the dissolution of both polymer and drug in a water-miscible organic solvent such as acetonitrile, acetone, dimethylformamide, or ethanol. Then, the polymer-drug solution is dialyzed against water. As the organic... 

The presence of dissolved gases in the involved solutions, which may be released during the coalescence of solution due to their solubility. This aspect becomes more severe in concentrated solutions and water-miscible organic solvents and/or when the system is operated under negative pressure (see also 5.4). The process used to obtain distilled-deionised water in the laboratory for reagent preparation can also have an effect ... 

It is easy to destroy micellar systems irreversibly by adding water-miscible organic solvents such as, e.g., acetone and ethanol. This technique is exceptionally effective and convenient when it is important to extract the solubilized protein (enzyme) delicately so that it retains its structure and physiological (including catalytic) activity [28]. Here, it should be emphasized that, first, the ethanol and especially acetone should be cold. Second, during precipitation with acetone in neutral and basic media, formation of Schiff bases is possible besides which, side reactions involving modification of the protein subjected to isolation (including the loss of the protein solubility in water) are also probable. 

Precipitation into submicron-sized particles is another direct approach. Precipitation by pH shifting can be an effective approach for dyes that have weak acid functionality. A number of different families of such dyes have been dispersed by acidification of weakly alkaline dye solutions, in the presence of stabilizers such as surfactants and polymers. Alternatively, solvent shifting has been demonstrated to be an effective method of preparing absorber dye dispersions. Recent work by Brick et al. (14) has shown how such dyes can be very effectively precipitated from a variety of water-miscible organic solvents. Finally, another approach for incorporation of absorber dyes is to precipitate or condense them on the surface of a high-surface-area carrier species, such as colloidal silica. Such preparations can be prepared by pH- and solvent-shifting processes, in the presence of the carrier particles. 

A more general use of proteolytic enzymes in peptide synthesis became feasible with the discovery (Sealock and Laskowsky 1969) of the effect of water miscible organic solvents on the equilibrium in enzyme catalyzed peptide bond hydrolysis and synthesis. In the presence of isopropanol (or dimethylfor-mamide, etc.) the dissociation of the carboxyl group is suppressed and, at least in a selected pH region, the equilibrium is shifted toward synthesis. A notable case is the conversion of porcine insulin to human insulin. Enzymatic cleavage of the C-terminal residue of the B-chain (alanine) with carboxypeptidase yields desalanino pork insulin. This cleavage is followed by the incorporation of... 

Partially water-miscible organic solvents (PMOSs) may act as either cosolvents or cosolutes, and the research in the past has shown flic complexity of their effects. " It was demonstrated that in order to exert effects on solubility or sorption of HOCs, PMOSs must exist as a component of the solvent mixture in an appreciable amount Munz and Roberts suggested a mole fi action of greater than 0.005 and Rao and coworkers proposed a volume percent of 1% or a concentration above lO mg/L. Cosolvents with relatively high water solubility are likely to demonstrate observable effects on the solubilities of solutes, up to their solubility limits, in a similar manner to cosolvents of complete miscibility with water. A few experimental examples of the effects of PMOSs include 1 -butanol and... 

Alternatively, the addition of polar solvents to hydrocarbon-based paints will improve the solubility of the thickener molecules, and decrease the chance of particles or clusters of molecules forming because of borderline solubility. This will lessen or even remove the effectiveness of the thickener. Again the same principles apply to aqueous coatings additions of water-miscible organic solvents (e.g. ether-alcohols) increase the solvency of the medium for the hydrophobic portions of the associative thickeners and lessen their tendency to associate. 

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