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Buffer exchange changes the small components surrounding a retained macromolecule toward those of a desired buffer solution. Components absent from fresh dialysate tend to leave; supplied components can enter. Each permeant solute has its own exchange problem.^[ref]

For a dilute, nonbinding permeant solute, an ideal equilibrium calculation approaches the bath's specified concentration. That approximation need not describe a solute bound to a protein or a charged mixture with additional electrical constraints. Retaining a protein also does not by itself establish that its protein structure or catalytic function survives the change of buffer solution.