Proteins stability neutral salts

A second interfacially active component may also induce the surface activity of weakly surface-active proteins due to strong intermolecular interactions. Electrostatic interactions from anionic bile salts enhance the adsorption of cationic chitosan on emulsion droplets emulsified by using a mixture of phospholipids, cholesterol and such bile salts. Carrageenan interacts strongly with milk proteins, which is of importance in relation to the association to emulsions and to its application in stabilizing neutral dairy products. 

Protein catalyst stability is limited. This is one of major drawbacks of enzymes. They commonly require temperatures around ambient to perform (15-50°C), pH values around neutral (pH 5-9), and aqueous media. In addition, any number of system components or features such as salts, inhibitors, liquid-gas or liquid-solid interfaces, or mechanical stress can slow down or deactivate enzymes. Under almost any condition, native proteins, with their Gibbs free enthalpy of stability of just a few kilojoules per mole, are never far away from instability. In this book, we cover inhibitors (Chapter 5, Section 5.3) or impeding system parameters (Chapter 17) and successful attempts at broadening the choice of solvents (Chapter 12). 

The influence of protein denaturants (such as alcohols, urea and urea derivatives, and quaternary ammonium salts) on the stability of the compact-coil conformation of PMAA is also described. These protein denaturants, when added to aqueous solutions of PMAA, considerably limit the rate of the neutral hydrolysis of 1-benzoyl-3-phenyl-1,2,4-triazole. 

The conformational stability of biomolecules is greatly dependent on the solvent species. It is also affected by coexisting solutes such as salts (e.g., NaCl). The salt effects [47, 48, 49] on the solubility and the conformational stability of proteins in aqueous solutions are experimentally known to follow the order called the Hofmeister series. The series for anions is [S04 > CHsCOO" > Cl > Br > NOa" > CIOJ > 1 > CNS ], and that for cations is [(CH3)4N+ > NH > Rb+,K+,Na+, Cs+ > Li+ > Mg + > Ca + > Ba +j. In each of these series, the species to the left decrease the solubility of proteins and stabilize their native structures. The species to the right, on the contrary, increase the solubility and cause destabilization of the native structures. Though the Hofmeister series is not valid for acidic and basic proteins [50, 51], it is generally applicable to neutral proteins. The series, except for divalent cations, is also applicable to the other neutral substances such as benzene [52]. That is, the effects of monovalent ions on the solubility of various neutral substances follow the Hofmeister series. The microscopic mechanisms of these experimentally known properties, however, have not been elucidated yet. 

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