Tracer sedimentation equilibrium: a powerful tool for the quantitative characterization of macromolecular self- and hetero-associations in solution

During the last two decades the measurement and analysis of sedimentation equilibrium has been used increasingly as a method for characterizing intermolecular interactions in solution. More recently, a variant of this technique has been developed, in which a trace amount of a single solute component is labelled so that the concentration gradient of that component at sedimentation equilibrium may be measured independently of the gradients of all other components. The dependence of equilibrium tracer gradients upon solution composition may be readily interpreted in the context of models for self- and hetero-association of the labelled component, and, in the case of concentrated solutions, repulsive as well as attractive solute–solute interactions. We present a summary of experimental and analytic methods, a brief review of some previously published applications, and a preview of new applications demonstrating capabilities beyond those afforded by other current techniques for characterizing macromolecular associations in solution.

Thermal Diffusion of Weak Electrolytes: IV. Relationship between the Transported Enthalpies of the Ionic and Molecular Form of the Solute

It is established that during the thermal diffusion of weak electrolytes in dilute aqueous solution the total transported enthalpies of the molecular and ionic form of the solute component are practically identical.

Method for Structural Characterization of High Polymeric Networks by an Osmotic Pressure Technique

An apparatus was designed to measure the osmotic pressure of solvent-polymer systems. The method is unique in that semirigid polymers may be incorporated as the solute component without specimen fissures occurring from excessive solvent dilative action. The advantages of this technique are: high polymeric materials both elastomeric and plastic can be structurally characterized by the same technique; the calculated effective molecular weight of the polymer network will reflect a value consistent with the polymer's performance characteristics; and the method is only restricted to lyophilic polymer—solvent systems.