Solubilization of Particulate Proteins and Nonelectrolytes by Chaotropic Agents

Abstract

Abstract.-Chaotropic ions (those ions which favor the transfer of apolar groups to water) provide a highly effective means for the resolution of membranes and multicomponent enzymes and for increasing the water solubility of particulate proteins and nonelectrolytes. The action of chaotropic agents is related to their effect on the structure and lipophilicity of water.The meager water solubility of particulate proteins and many biological compounds such as hemes, purines and pyrimidines, nucleosides, certain vitamins, and various structures of pharmacological interest has posed considerable difficulty in the study of their chemical and biological properties. Also, because of the predominance of hydrophobic bonds in membranes and multicomponent enzymes, the stability of these systems in aqueous media has been a major impediment in attempts at their resolution and unraveling of their molecular organization and mechanism of action.Among the forces contributing to the stability of these structures in aqueous media, hydrophobic attractions are most significant. This is because van der Waals attractions between apolar groups are weak and hydrogen bonds of the C..O ... H-N and C.0O ... H-0 type are, according to Klotz and co-workers,1 thermodynamically unstable if not protected from water. Since hydrophobic attraction is in essence a water-repulsion force, a consideration of the factors that influence the expulsion of most nonelectrolytes and the apolar regions of particulate proteins from water might provide significant clues to methods for increasing the solubility of such structures in aqueous media.According to Kauzmann,2 apolar groups form hydrophobic bonds mainly as a result of their thermodynamically unfavorable interaction with water, rather than as a consequence of interaction with each other. Thus, the transfer of an apolar molecule from a lipophilic surrounding to water is endergonic by 2-6 keal per mole because of an associated unitary entropy2 decrease of 10-20 entropy units (eu). (See, for example, the negative AH and AS values in Table 1 for the transfer of a variety of simple nonelectrolytes from benzene to water.) This large, negative entropy difference appears to be almost entirely related to the structure of water3-5 and can be diminished by changing the structure of water in the direction of greater disorder. Our studies suggest that such a condition can be created in the presence of certain inorganic anions.As shown in Table 2, the hydrated forms of anions such as SCN-, C1O-4, I-, Br-, and Cl-are associated with large, positive entropies. A simple interpretation of this large entropy increase (see also the entropies of hydration in Table 2) is the possible effect of these ions on the structure of water. This interpretation is in agreement with the conclusions of Hamaguchi and Geiduschek,6 1129

Isoantigenicity of Rabbit Sperm, Testis, and Their Extracts as Demonstrated by Western Blot Enzyme Immunobinding Procedure

“…The variation in results from one detergent extract to another can be explained on the basis of differential solubilization and inactivation of various proteins in different detergents. For example, it is known that different chaotropic salts have wide ranges of effectiveness: potassium thocyanate releases only small portions of proteins from erythrocyte ghosts [5], guanidine hydrochloride releases all except one or two erythrocyte membrane proteins [19], and LIS brings about complete dissolution of the membrane [13]. However, use of these protein perturbants or chaotropic agents, which are weaker than detergents, does not lead to solubilization of proteins that are more strongly bound to the lipid matrix of the membrane.…”

The Action of Chaotropic Anions on the Sarcoplasmic Calcium Pump

“…It is thought to be primarily the result of their ability to disrupt the hydrogen -bonded structure of water whereby the hydrophobicity of the aqueous solvent is increased [5].…”

Transepithelial Bicarbonate Secretion: Lessons from the Pancreas

“…Bicarbonate in pancreatic juice and duodenal fluids neutralizes gastric acid and pro-vides an optimal pH environment for digestive enzymes to function properly in the duodenum (Lee and Muallem 2008). In addition, as a moderate chaotropic ion, bicarbonate facilitates the solubilization of macromolecules such as mucins (Hatefi and Hanstein 1969). Recent studies suggest that the abnormal bicarbonate secretion observed in cystic fibrosis (CF) leads to altered mucin hydration and solubilization (Quinton 2010), resulting in hyperviscous mucus that blocks ductal structures of the lung and pancreas (Quinton 2001(Quinton , 2008.…”