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Amino acid surfactants with solvents

Juang, R.S. and Wang, Y.Y. (2002). Amino acid separation with D2EHPA by solvent extraction and liquid surfactant membranes. J. Membr. Sci., 207, 241-52. [Pg.197]

Cosolvents ana Surfactants Many nonvolatile polar substances cannot be dissolved at moderate temperatures in nonpolar fluids such as CO9. Cosolvents (also called entrainers, modifiers, moderators) such as alcohols and acetone have been added to fluids to raise the solvent strength. The addition of only 2 mol % of the complexing agent tri-/i-butyl phosphate (TBP) to CO9 increases the solubility ofnydro-quinone by a factor of 250 due to Lewis acid-base interactions. Veiy recently, surfac tants have been used to form reverse micelles, microemulsions, and polymeric latexes in SCFs including CO9. These organized molecular assemblies can dissolve hydrophilic solutes and ionic species such as amino acids and even proteins. Examples of surfactant tails which interact favorably with CO9 include fluoroethers, fluoroacrylates, fluoroalkanes, propylene oxides, and siloxanes. [Pg.2002]

Esters represent an important class of chemical compounds with applications as solvents, plasticizers, flavors and fragrances, pesticides, medicinals, surfactants, chemical intermediates, and monomers for resins. Recently, esters of amino acids have attracted attention regarding their use as biobased surfactants with excellent adsorption and aggregation properties, low toxicity, and broad biological activity. [Pg.373]

The peptide chain in globular proteins is folded into fairly compact conformations. Water-soluble enzymes are typical globular proteins which have most of the hydrophobic amino acid residues located in the interior and the hydrophilic residues located mainly at the surface in contact with solvent water. The average radii are 20-40 A (Boyer, 1970). It is clear that there are common morphological features between surfactant micelles and enzyme molecules. This fact has prompted many chemists to use micelles as enzyme models. However, it must be emphasized that micelles exist in dynamic equilibria with monomeric surfactant and their hydrophobic core is quite fluid, whereas enzyme molecules have precisely fixed three-dimensional structures. [Pg.437]

The mechanism of separation of biological molecules such as proteins and amino acids, and the parameters that affect the extraction distribution coefficient and the kinetics of extraction have been studied more extensively than the extraction of inorganic solutes. This is mainly due to the variety of size and structure of these molecules and, furthermore, to the fact that their characteristics may be adversely affected by their contact with solvents and surfactants. [Pg.663]

Polypeptides adopting a 3-structure exhibit CD spectra, the characteristic features of which are a negative band at about 216 nm ([ ] = -18,000) and a positive band of comparable magnitude near 195 nm (Figure 2). However, the CD spectra of (3-struc-tures show much more pronounced variations with solvent and amino acid residues than those of the a-helix, both in amplitude and in the position of the bands. In the presence of sodium dodecyl sulfate, the (3-form of poly(L-lysine), though still a 13-structure by infrared criteria, gives a 218 nm CD band only about half as large as that in the absence of the surfactant.[11]... [Pg.403]

Kraak, J.C., Jonker, K.M., and Huher, J.F.K. Solvent-generated ion exchange systems with anionic surfactant for rapid separation of amino acids. J. Chmmatogr. 1977, 142, 671-688. [Pg.51]

J. C. Kraak, K. M. Jonker, and J. E K. Huber, Solvent-generated ion-exchange systems with anionic surfactants for rapid separations of amino acids, /. Chromatogr. 142 (1977), 671-688. [Pg.235]

Selection of the most suitable organic solvent should consider the polarity of analytes and their association with the surfactant. Solute log Fo/w values can be used, in most cases, as a guide to make this decision.Thus, with SDS as surfactant, a low concentration of propanol ( 1% v/v) is useful to separate compounds with log Po/w < 1 as amino acids. A greater concentration of this solvent ( 5% to 1%) is needed for compounds in the range 1 < log Po/w < 2 as diuretics and sulfonamides. Pentanol ( 2% to 6%) is more convenient for low polar compounds with log Po/w > 3 as steroids. For basic compounds, such as phenethylamines with 0electrostatic interaction between the positively charged solutes and the anionic surfactant adsorbed on the stationary phase. In this case, a high concentration of propanol ( 15%), or preferably, a moderate concentration of butanol (<10%) should be used. [Pg.811]

One of the most successful asymmetric catalytic reactions is the asymmetric hydrogenation of amino acid precursors by means of optically active rho-dium(I)phosphine or phosphinite complexes [55]. Usually, the reaction is carried out in methanol as solvent. When water is used the activity and enantiose-lectivity decrease significantly [16], but the addition of micelle forming surfactants leads to a solubilization of catalyst and substrate and increases activity and enantioselectivity. The results are somewhat better than the ones obtained with methanol as solvent [56]. Table 2 shows the effect with different types of surfactants. [Pg.1301]

Crown ethers also enhance the activity of enzymes in organic solvents.100 The enzyme is lyophilized in the presence of the crown ether before use. a-Chymotrypsin treated in this way with 18-crown-6 was 640 times as active in transesterification of amino acid esters as the untreated enzyme. However, the rate was still 50 times lower than in water. The use of surfactants to improve activity in organic solvents seems preferable because of a greater rate increase. They also avoid the toxicity and expense of the crown ethers. The cross-linked enzyme crystals also offer a way to obtain reasonable rates in organic solvents. [Pg.247]


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See also in sourсe #XX -- [ Pg.209 ]




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