Segmental diffusion correlation distance

The expression (y — 1)/(Dm ) allows one to calculate xU) easily from the simulation parameters, and the expression x j) Dt allows one to correlate the properties of boxy with the properties of the experimental solution segment situated at a real distance c from a physical electrode. Note that xU) is the ratio of actual distance to the diffusion length (D k) for the characteristic time t. ... 

Scatchard s equation (1946) is derived to explain Ai for proteins. The change in dimensions (e.g., mean-square end-to-end distance) is not of any concern in Scatchard s derivation. No model was assumed and no statistical mechanics was used. Scatchard successfully correlated the osmotic pressure with the distribution of diffusible solutes across a semipermeable membrane by manipulating the terms of activities of the components (such as protein, salt, and water) with changing composition of the solutions. The mathematical detail is simple but messy. According to Scatchard, the interactions involved in protein solutions are not limited to the exclusion of volume between the segments of macromolecules but also includes the Donnan effect and the binding of small ions to macro ions in a given system. For simplicity, let us consider a three-component system, and let 1 represent the solvent (or buffer), 2 the macromolecule (such as protein), and 3 a salt (e.g., NaCl). Scatchard derived an equation of the second vitial coefficient... 

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