Interactions of Small Ions with Heparin and Dextran Sulfate by Self-Diffusion Measurements

Abstract

These results show that the extent of branching for these star-shaped materials increases with reaction time and that the maximum extent of branching is not reached until the later stages of the reaction. In other words, the star formation process involves, at least in part, the addition of unlinked (or perhaps coupled) parent material to branched polymer. These observations are in accord with the divinylbenzene linking reaction characteristics discussed previously.

Sodium Ion Diffusion Coefficients in Aqueous Salt-Free Polyelectrolyte Solutions

“…This method has been described previously. 10 The following expression was used to determine the diffusion coefficients23 C/C°= (8/7 2) ¿ [exp(-(2n + l)VDt/4L2)]/(2n + l)2 (6) -0 where D = DNa+, the sodium ion self-diffusion coefficient for the labeled species, t is the time allowed for diffusion, L is the capillary length, C is the radioactive content of the capillary after diffusion has taken place, and C°is the radioactive content of the capillary prior to diffusion taking place. Previous studies used an approximate solution of eq 624 = (ir/4)(1 -C/C°)2(L2/t) (7) However, because of the approximation used in deriving eq 7, the lower the ratio of C/C°u sed the higher is the error in DNa+.…”

Complexes of natural carbohydrates with metal cations

“…345 This corresponds to the normal behaviour of polyelectrolytes in which s-metal cations are bound non-specifically (territorial binding, Section II.1). In other words, they merely `condense' on the negative charges in the polymeric chain, 346,347 according to the Manning theory. 78 However, in another study, 348 specific binding of Na + by two carboxyl groups of the neighbouring L-iduronic acid residues was suggested, based on the results obtained by 23 Na NMR spectroscopy.…”

Counterion binding in polyelectrolyte theory

“…If the self-diffusion coefficient of a small counterion is observed to be equal to that of a much larger polyion, for example, the counterion may be considered bound to the polyion. [1][2][3][4] In favorable cases, frequently encountered in practice, the close approach of a counterion and polyion occurs with mutual perturbation of hydration layers; the resulting volume changes can be either measured directly by volumetric instrumenta-tion5-8 or probed by ultrasonic absorption9-11 or index of refraction measurements.12 Counterions passing from a state of free hydration into an environment of perturbed hydration, as detected by these techniques, are said to pass from a free to a bound state. Magnetic and spin resonance signals are sensitive to the close approach of a polyion and a counterion; counterions giving rise to signals altered from a standard reference state (absence of polyion, for example) can be called bound to the polyion.…”