Enhancement of stability

Klang, V., Matsko, N., Zimmermann, A.M., Vojnikovic, E. and Valenta, C. (2010) Enhancement of stability and skin permeation by sucrose stearate and cydodextrins in progesterone nanoemulsions. International Journal of Pharmaceutics, 393, 152—160. 

Some modifications to the cyclodextrin structure have also been found to improve their complexing ability. Casu and coworkers prepared 2,3,6-tri-O-methyl and 2,6-di-O-methyl derivatives of alpha and beta cyclodextrin. They observed that tri-O-methyl-alpha cyclodextrin shows an almost ten-fold increased stability of the complex with the guest, Methyl Orange, compared with the unmodified alpha cyclodextrin. A possible reason for this increase in stability is that the methyl groups are responsible for an extension of the hydrophobic cavity of the cyclodextrin. Other workers,however, observed a much smaller enhancement of stability of complexes on methylation of the cyclodextrin, and a decrease in stability has even been reportedfor the one host-two guests complex of tropaeolin with beta cyclodextrin. Thus, the effect of methylation on the stability of a complex varies with the guest species involved, and cannot be readily predicted. 

An enhancement of stability due to the contracted conformation of a polymer-ligand chain may also be deduced from Table 5. The (34 value of a PAA-Cu chelate is larger in the system with higher ionic strength. The interpretation is that the local concentration of ligands is increased by the contraction of the PAA chain on the addition of the neutral salts°). 

Enhancement of Stability of Proteases against Oxidation and Thermal Deactivation 293... 

The Irving-Williams order results from an enhancement of stabilities for complexes formed with Fe, Co " ", and Cu2+... 

A spectacular example of stability enhancement through immobilization has been reported for the enzyme catechol-2,3-dioxygenase.27 This enzyme, isolated from the thermophilic bacterium Bacillus stearothermophilus, catalyzes the conversion of catechol to 2-hydroxymuconic semialdehyde (which can be monitored by absorbance at 375 nm). The soluble enzyme exhibits maximal activity at 50 °C, but following immobilization on glyoxyl agarose beads with a borohydride reduction step, the optimum reaction temperature shifted to 70 °C. At a total protein concentration of 0.010 mg/mL and a temperature of 55 °C, the half-life of the soluble enzyme was 0.08 h, while the enzyme-modified beads had a half-life of 68 h. This represents a 750-fold enhancement of stability that has been attributed to the prevention of subunit dissociation upon immobilization. 

Zejtli, J., Bolla-Pusztai, E., Szab6, P, and Ferenczy, T. (1980) Enhancement of stability and biological effect of cholecalciferol by P-cyclodextrin complexation, Pharmazie, 35, 779-787. 

Suppressing of shrinkage and felting, enhancement of stability with respect to fabric wear-out Wool... 

Stabilities of complexes between open-chain pentaethers and alkali metal ions Enhancement of stabilities by attaching quinoline moieties as donor end groups (from Ref. )... 

An enhancement of stabilization was obtained by using CTM A-Cl, which allows high solid contents and the synthesis of very small particles with diameters <100 nm. However, CTMA-Cl was chosen as a cross-test to highlight the deficiencies of the system, since its use is prohibited by demands of biocompatibility and biodegradability. 

---