On the use of the activation energy concept to investigate analyte and network deformations in entangled polymer solution capillary electrophoresis of synthetic polyelectrolytes

Abstract

The activation energy associated with the electrophoretic migration of an analyte under given electrolyte conditions can be accessed through the determination of the analyte electrophoretic mobility at various temperatures. In the case of the electrophoretic separation of polyelectrolytes in the presence of an entangled polymer network, activation energy can be regarded as the energy needed by the analyte to overcome the obstacles created by the separating network. Any deformation undergone by the analyte or the network is expected to induce a decrease in the activation energy. In this work, the electrophoretic mobilities of poly(styrenesulfonates) (PSSs) of various molecular weights (Mr 16 x 10(3) to 990 x 10(3)) were determined in entangled polyethylene oxide (PEO) solutions as a function of temperature (in the 17-60 degrees C range) and the PSS activation energies were calculated. The influences of the PSS molecular weight, blob sizes zetab of the separating network (related to the PEO concentration), ionic strength of the electrolyte and electric field strength (75-600 V/cm) were investigated. The results were interpreted in terms of analyte and network deformations and were confronted with those previously obtained for DNA migration in polymer solutions and chemical gels. For a radius of gyration Rg<zetab the activation energy increases with the PSS molecular mass, while the reverse is true for Rg>zetab, suggesting PSS and network deformations in the latter case. Increasing ionic strength resulted in an increase in the PSS activation energy, because of the decrease of their radii of gyration, which makes them less deformable. Finally, the activation energies of all the PSSs are a decreasing function of field strength and at high field strength tend to reach a constant value close to that for a small molecule.

On the electromigration of charged fluorophore‐labeled oligosaccharides in polyethylene oxide solutions

“…with increasing network formation, significant monotonic decreases were observed in the activation energy values with increasing solute size. As Cottet and Gareil [7] suggested in their landmark publication, decrease in the activation energy as a function of the solute size may suggest solute and/or polymer matrix deformation; however, possible solute-matrix interactions should also be considered [10] with potential influence on the activation energy requirement. Important to note that the absolute activation energy requirement for all solute sizes increased with the PEO concentration of the separation medium, for example for DP = 1 from 15.7 kJ/mol at 0% PEO to 24.2 kJ/mol at 2% PEO.…”

“…Nowadays, in CGE, almost exclusively physical gels (chemically noncross-linked polymer solutions) are used as separation matrices, typically above but sometimes even below their entanglement threshold [6]. Thus, network configuration, including any possible deformation [7], as well as possible physical-chemical parameters such as the composition of BGE, separation temperature, molecular characteristics of the solute molecules, etc., should be considered when the electromigration process of sugars is investigated. In addition to the polymer network, the analytes can also be subject to structural deformations during their electrophoretic migration.…”

Activation energy associated with the electromigration of oligosaccharides through viscosity modifier and polymeric additive containing background electrolytes

“…CE has been extensively used for physicochemical characterization of biopolymers, such as nucleic acids, proteins, and carbohydrates using cross‐linked gels or linear polymer matrices . Based on the fact that the separation mechanism of biopolymers in linear polymer networks are similar to that of in cross‐linked gels, and due to the difficulties of working with chemical gels in narrow bore capillary tubings, today almost exclusively physical gels are used in CE.…”

“…The activation energy can be considered as the energy required by the analyte molecules to overcome the obstacles created by the separation medium. As a general assumption, the larger the analyte molecule, the higher the energy required to pass through the network, as long as no deformation occurs . Early reports discussed the influence of temperature in size‐based separation of biopolymers , but the activation energy concept was first applied to this field by Guttman and Cooke for the separation of double‐stranded DNA fragments under isoelectric and isorheic separation conditions .…”

“…Understanding the activation energy requirement of the analyte molecules migrating through the BGE (viscous, polymeric, or both) will give us a better insight into the effect of viscosity and possible solute polymer‐matrix interaction. Cottet and Gareil suggested that deformation of the analyte or the separation matrix is expected to decrease the activation energy. Concomitantly, measuring the activation energy changes can provide important information about any matrix or solute deformations.…”