A ligand binding model of counterion condensation to finite length polyelectrolytes

✍ Scribed by T. G. Dewey

• Publisher: Wiley (John Wiley & Sons)
• Year: 1990
• Tongue: English
• Weight: 551 KB
• Volume: 29
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.360291410

✦ Synopsis

A ligand binding model of counterion association in finite length polyelectrolytes is presented. This model introduces counterion condensation features into a binding formalism. It agrees well with the predictions of other finite length models and is consistent with experimental data on helix-coil melting transitions for short nucleic acid oligomers. This model uses a discrete charge distribution for the polyelectrolyte. An expression for the electrostatic self-energy of finite length polyelectrolytes is derived using the Euler-Maclaurin sum formula. This sum is shown to be accurate over a wide range of salt concentrations. This electrostatic term is used in an energy minimization analysis. The energy minimization is solved analytically using a Lagrange inversion formula. This general procedure gives a rapidly convergent series and requires no assumptions with regard to "limiting law" behavior. However, when used in the Manning minimization formalism [ ( 1977) Biophysical Chemistry, 24, 20861, the volume of the condensed phase becomes unrealistically large at low ionic strength. The ligand binding model does not have a condensed phase volume as a parameter. It provides a single expression that agrees both with Manning's theory and with the theory of Ramanathan and Woodbury [ (1982) Journal of Chemical Physics 77, 41331 under the respective conditions of these theories.