PubMed · 5190060
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M Shimizu. 1968. [Electrolyte solutions].. https://pubmed.ncbi.nlm.nih.gov/5190060/
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The Dukhin-Deryaguin equation, used in the modern theory of electrophoresis for the calculation of electrophoretic mobility (EPM) in the region of double layer polarization, is known from literature [4-6] in its form (DD1) valid for the equal mobilities of the cation and anion in solutions of symmetrical electrolytes. Here we describe the other version of this equation (DD2), for arbitrary ion mobilities in 1:1 electrolytes. The EPMs calculated from this latter version are in good agreement with an exact computer solution [12]. The use of DD2 is illustrated in a series of EMP vs. IgC curves, calculated for selected examples of negatively charged lipid membranes. In addition, we describe two simplified versions of DD2, which are valid, respectively, for the high zeta potentials and when the electroosmotic component of ions' fluxes at the charged surface is neglected. Comparing DD2 with DD1 shows that the latter equation results in an error which may exceed the experimental dispersion of EPM values in the absence of specific ion binding. This error is reduced if the counter-ion binding is not small; hence, DD1 may also be used in some cases for solutions with arbitrary ion mobilities.
Coulombic interactions of salt ions with polymeric and oligomeric nucleic acids in solution have large and distinctive effects on ion distributions, on thermodynamic coefficients, and hence on equilibrium processes involving nucleic acids, such as their conformational transitions and binding interactions. In experimental or theoretical studies where an oligonucleotide is taken to represent the corresponding polynucleotide, the impact of coulombic end effects on molecular and thermodynamic properties must be taken into account. Observable consequences of coulombic interactions in nucleic acid solutions have been calculated by using models with varying degrees of detail and methods formulated at varying levels of rigor. From comparisons of experimental results with predictions of the prevalent theoretical approaches, this review concludes that the more rigorous methods have proved capable of accounting for thermodynamic (and some molecular) consequences of coulombic interactions with a minimal number of preaveraged parameters that represent the most important structural features of the nucleic acid solution.
A method for the determination of the (6R)- and (6S)-stereoisomers of leucovorin using electrokinetic chromatography (EKC) in the affinity mode has been developed. Bovine serum albumin (BSA) is used as a run buffer additive to incorporate enantiomeric selectivity into the system. Protein-wall interactions are minimized by using a poly(ethylene glycol) (PEG) coated capillary. Chiral resolution is obtained in 12.5 min with efficiencies greater than 200,000 theoretical plates using BSA as an additive, while no resolution is obtained in the absence of BSA. A general equation is derived to calculate the free energy of interaction between the leucovorin isomers and the BSA molecule. This method represents a new means of obtaining thermodynamic data for substrate binding interactions and for the general study of drug cross-reactions and interactions of drugs with serum and other proteins.