| Abstract
| - A number of studies have shown the suitability of the polyelectrolyte model to describe the proton-bindingbehavior of macromolecules. This model, however, has two limitations associated with its theoreticalapproach: (1) it does not consider the possible heterogeneity of binding sites, and (2) for certain calculations,it involves the need to assume a specific molecular geometry. In this article we describe the theoretical basisof an extension of the polyelectrolyte model that removes the two limitations described above. Likewise, wediscuss the advantages and limitations of the extended polyelectrolyte model (EPM) through its applicationto describe the proton-binding process in a well-characterized macromolecular system (a poly(acrylic acid))and a complex molecular system (a humic acid). The results obtained showed the suitability of EPM todescribe proton-binding processes in complex molecular systems without the need to assume previously aspecific molecular geometry and explicitly considering the possible heterogeneity of the binding sites. Theresults obtained indicated that the field effects associated with the conformational structure corresponding toeach ionic strength, even in the discharged state, affect the values of the intrinsic constants defining theproton-binding process using EPM. Likewise, EPM analysis reveals the significant influence of both thesurface charge density and the molecular size on the value of the electrostatic effects affecting the values ofthe intrinsic constants in the proton-binding process.
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