Water-cosolvent systems

Timasheff, S.N. (1982). Preferential interactions in protein-water-cosolvent systems. In Biophysics of Water, ed. F. Franks, pp. 70-2. London John Wiley. 

Wittaya-areekul, S., Nail, S.L. Freezedrying of tert-butyl alcohol/water cosolvent systems effeects of formulation and process variables on residual solvents. J. Pharm. Sci. 87,491-495,1998... 

If a drug is a weak acid, the concentrations of the un-ionized species, [HA]C, and the ionized species, [A ]c, in a water/cosolvent system are in equilibrium and the total solubility, [HA])ot, in the water/cosolvent system is given by ... 

The total solubility of weak acid in a water/cosolvent system [HA] ot can be determined by the solubility of the un-ionized species in water, the solubilizing powers, the hydrogen ion concentration, and the dissociation constant of the weak acid. Equation (3.49d) illustrates that the total solubility of the weak acid will increase exponentially with respect to the volume fraction of the cosolvent. Even though the solubilizing power of the cosolvent for the un-ionized species is usually larger than that of the ionized species, the solubilization of the ionized species is very important in determining the total solubility when pH - pKa > oIIA - oa. ... 

Megrab NA, Williams AC, and Barry BW. Oestradiol Permeation Across Human Skin, Silastic and Snake Skin Membranes the Effects of Ethanol/Water cosolvent Systems. IntJPharm 1995 116 101—112. 

FIGURE 39.4 Solubility of the free base and the hydrochloride of dexoxadrol at 23°C in a water-cosolvent system, as a function of the percentage of the cosolvent, PEG 300. 

The behavior of aminoacylase both from porcine kidney and Aspergillus sp. towards a wide range of water-miscible cosolvents was investigated by Iborra et al.1661. They found that enzymatic activity can be correlated with the denaturing capacity of the water-cosolvent system. 

The use of the Wilson equation for liquid-liquid equihbrium is unusual because the equation cannot predict phase separation. In the present application the equation is not being used to predict immiscibility-the organic and water phase are assumed to be immiscible. The Wilson equation is used instead to correlate activity coefficients in the miscible range for the hydrocarbon-cosolvent and water-cosolvent systems. 

Erbeldinger M, Ni X, HaUing PJ (1998) Effect of water and enzyme concentration on thennolysin-catalyzed solid-to-sohd peptide synthesis. Biotechnol Bioeng 59(l) 68-72 Fernandez-Lafuente R, Alvaro G, Blanco RM et al. (1991) EquUibrium controlled synthesis of cephalotin in water-cosolvent systems by stabiDzed peniciUin acylase. Appl Biochem Biotechnol 27 277-289... 

These systems were tested in the enzymatic aldolization of a variety of A/-Cbz-aminoaldehydes catalyzed by D-fructose-l,6-bisphosphate aldolase from rabbit muscle (RAMA) and L-rhamnulose-1-phosphate aldolase and L-fuculose-1-phosphate aldolase from E. coli (Espelt et al. 2003 a,b, 2005). The largest differences between conventional DMF/water cosolvent systems and gel emulsions were observed with RAMA catalyst (Fig. 6.5.11). 

Figure 14.21.2.2a. Deviations from log-linear model (equation [14.21.2.2], triangle) and the extended log-linear model (equation [14.21.2.10], circle) for solute naphthalene in various water cosolvent systems. Experimental data are from Ref. 83.

Table 14.21.2.3. UNIFAC derived water-cosolvent systems...

S Wittaya-Areekul, GF Needham, N Milton, ML Roy, SL Nail. Freeze-drying of /er/-butanol/water cosolvent systems a case report on formation of a friable freeze-dried powder of tobramycin sulfate. Journal of Pharmaceutical Sciences 91 1147-1155, 2002. 

C01 Cowie, J.M.G., Mohain, M.A., and McEwen, I.J., Alcohol-water cosolvent systems for poly(methyl methacrylate), Po/ywer, 28,1569,1987. 

Cowie JMG, Mohsin MA, McEwen U (1987) Alcohol water cosolvent systems for poly (methyl methacrylate). Polymer 28(9) 1569-1572. doi 10.1016/0032-3861(87)90360-0... 

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