Modeling the electrophoresis of oligolysines

Abstract

CE is used to measure the electrophoretic mobility of low molecular mass oligo-L-lysines (n=1-8) in aqueous LiH₂PO₄ buffer, BGE, at pH 2.5 over a range of temperatures (25-50 °C) and ionic strengths (10-100 mM). Mobilities are corrected for Joule heating and under the conditions of the experiment, interaction of the peptides with the capillary walls can be ignored. A "coarse grained" bead modeling methodology (BMM) (H. Pei et al., J. Chromatogr. A 2009, 1216, 1908-1916) is used to model the mobilities. This model partially accounts for peptide conformation as well as the assumed form of its secondary structure. For highly charged oligolysines, it is necessary to properly account for the relaxation effect. In the present study, the BMM approach tends to overestimate oligolysine mobility and that effect tends to increase with increasing ionic strength and peptide length. It is proposed that association between the oligolysines and buffer components (H₂PO₄⁻ in this case) that go beyond classical electrostatic interactions are responsible for this discrepancy. A simple binding model is introduced that illustrates how this association can reconcile model and experiment.

Generalized polymer effective charge measurement by capillary isotachophoresis

“…This approach is well suited for small ions and nanoparticles (hardcore charged spheres) but is not yet applicable to polyelectrolytes due to the lack of suitable theoretical model. Numerical simulations can also be used [26][27][28][29][30][31] but these approaches are computationally time consuming and, as a consequence, limited so far to the study of oligomeric chains.…”

Modeling the electrophoresis of highly charged peptides: Application to oligolysines

“…The experimental mobilities of oligolysines in lithium phosphate BGE at different temperatures have been reported previously 17 and these data shall be used in the present analysis. Experimental mobilities have been corrected for electroosmotic flow as well as Joule heating.…”

“…Experimental mobilities have been corrected for electroosmotic flow as well as Joule heating. Modeling of weakly charged peptides has been described in detail previously 12–17, and much of that development can also be applied to highly charged peptides. In the present work, the underlying modeling is only briefly described.…”

“…A peptide made of n amino acids is modeled as 2 n non‐overlapping beads and account can be taken of both peptide primary and secondary structure 14. Until now, electrostatics in the BMM approach, with the exception of the “large ion” relaxation correction 17, has been treated at the level of the linear Poisson–Boltzmann, LPB, and equation. Provided the peptides are weakly charged, this is expected to be a reasonable approximation of electrostatics.…”

Specific ion effects on the electrophoretic mobility of small, highly charged peptides: A modeling study

“…In recent years, numerous investigators employing a variety of modeling strategies have analyzed free solution CE mobility data of peptides in an attempt to determine their physicochemical properties and, in some cases, elucidate their structure . Our laboratory has played a part in these studies by developing a coarse‐grained bead modeling methodology (BMM) that partially accounts for the finite extent of peptides in modeling their electrophoretic mobility . Initially designed for weakly charged peptides where electrostatics are solved at the level of the linear Poisson–Boltzmann (PB) equation, it was subsequently generalized to solve the electrostatics at the level of the no linear PB equation, the BMM‐NLPB procedure, to make it applicable to highly charged peptides .…”