title: Rate-of-dialysis technique: theoretical and practical aspects.
abstract: In the rate-of-dialysis technique, chemical equilibrium exists throughout the experiment between the contents of the two halves of a dialysis cell. Initially, however, a trace amount of labeled dialysand is present in one of the half-cells, and the dialysis of that is followed as a function of time. The method is able to reveal whether a compound is stable under the conditions used or whether it is affected, for example, by aggregation, precipitation, oxidation, or hydrolysis. The rate constants for six inorganic ions and 22 organic molecules were determined, and no simple relations were found between rate constants and functions of molar masses. However, in two homologous series of compounds, a linear relationship between rate constant and molar mass was found, allowing for a preliminary identification of an unknown substance. Whether the presence of a macromolecule results in binding of the dialysand is easily tested for because in that case its rate constant is sharply diminished. High-affinity binding was studied using octanoate and laurate as ligands and human serum albumin as binding protein. The primary binding constants determined were similar to those obtained by equilibrium dialysis. However, the rate-of-dialysis technique is much faster, and its results are less scattered. The technique is well suited for binding studies performed with high protein concentrations because it is not affected by any osmosis or Donnan effects.
authors.affiliation: Institute of Medical Biochemistry, University of Aarhus, Ole Worms Allé, Building 170, DK-8000 Arhus C, Denmark. ukh@biokemi.au.dk
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kragh-Hansen
authors.forename: Evy
authors.initials: E
authors.lastname: Dørge
authors.forename: Anders Overgaard
authors.initials: AO
authors.lastname: Pedersen
mesh_terms: D002210:Caprylates / Q000378:metabolism; D003956:Dialysis / Q000379:methods*; D006801:Humans; D007553:Isotope Labeling; D007700:Kinetics; D007850:Lauric Acids / Q000378:metabolism; D008024:Ligands; D019814:Myristic Acid / Q000378:metabolism; D019308:Palmitic Acid / Q000378:metabolism; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D002210:Caprylates; D007850:Lauric Acids; D008024:Ligands; D012709:Serum Albumin; D019814:Myristic Acid; C030358:lauric acid; D019308:Palmitic Acid; C031492:octanoic acid