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A KATCHALSKY

Publications and source records attributed to A KATCHALSKY.

18 recordsLinked to original sources
PubMed1964

POLYELECTROLYTES AND THEIR BIOLOGICAL INTERACTIONS.

Polyelectrolytes are water-soluble electrically charged polymers. Their properties are determined by the interplay of the electrical forces, the Brownian motion of the macromolecular chain, and intermolecular Van der Waals forces. Charged polyacids or polybases are stretched by the electrostatic forces, as evidenced by increase in solution viscosity, or by the stretching of polyelectrolyte gels. The electrical field of the polyions is neutralized by a dense atmosphere of counter-ions. The counter-ion attraction to the polyions is expressed by a reduction of the osmotic activity of the polyion-the osmotic pressure being only 15 to 20 per cent of the ideal in highly charged polyelectrolytes neutralized by monovalent counter-ions, and as low as 1 to 3 per cent of the ideal for polyvalent counter-ions. Since the ionic atmosphere is only slightly dependent on added low molecular salt, the osmotic pressure of polyelectrolyte salt mixtures is approximately equal to the sum of the osmotic pressure of polyelectrolyte and salt alone. Acidic and basic polyelectrolytes interact electrostatically with precipitation at the point of polymeric electroneutrality. At higher salt concentrations the interaction is inhibited by the screening of polymeric fixed charges. The importance of these interactions in enzymatic processes is discussed. The electrical double layer is polarizable as may be deduced from dielectric and conductometric studies. The polarizability leads to strong dipole formation in an electrical field. These macromolecular dipoles may play a role in the adsorption of polyelectrolytes on charged surfaces. The final part of the paper is devoted to interactions of polyelectrolytes with cell membranes and the gluing of cells to higher aggregates by charged biocolloids.

Adsorption↗
PubMed1963

THE FRICTIONAL COEFFICIENTS OF THE FLOWS OF NON-ELECTROLYTES THROUGH ARTIFICIAL MEMBRANES.

The phenomenological permeation coefficients were determined for two artificial cellulose membranes of known thickness and water content. Transport of non-electrolytes was studied with tagged water, urea, glucose, and sucrose. The effect of the unstirred layers on the experimental determination of the coefficients is discussed. Frictional coefficients between membrane matrix and solutes, and between solvent and solutes in the membrane are calculated. It was shown that the geometrical tortuosity does not correspond to a physical tortuosity.

Biological Transport↗
PubMed1961

A physical interpretation of the phenomenological coefficients of membrane permeability.

A "translation" of the phenomenological permeability coefficients into friction and distribution coefficients amenable to physical interpretation is presented. Expressions are obtained for the solute permeability coefficient omega and the reflection coefficient sigma for both non-electrolytic and electrolytic permeants. An analysis of the coefficients is given for loose membranes as well as for dense natural membranes where transport may go through capillaries or by solution in the lipoid parts of the membrane. Water diffusion and filtration and the relation between these and capillary pore radius of the membrane are discussed. For the permeation of ions through the charged membranes equations are developed for the case of zero electrical current in the membrane. The correlation of sigma with omega and L(p) for electrolytes resembles that for non-electrolytes. In this case omega and sigma depend markedly on ion concentration and on the charge density of the membrane. The reflection coefficient may assume negative values indicating anomalous osmosis. An analysis of the phenomena of anomalous osmosis was carried out for the model of Teorell and Meyer and Sievers and the results agree with the experimental data of Loeb and of Grim and Sollner. A set of equations and reference curves are presented for the evaluation of omega and sigma in the transport of polyvalent ions through charged membranes.

Biological Transport↗