Peptide chain characterization via capillary electrophoresis for low and high particle electrokinetic potentials

MARTA B. PEIROTTI; MARÍA V. PIAGGIO; JULIO A. DEIBER

Los Cocos - Córdoba

Simposio; XII Simposio Argentino de Polímeros - SAP 2017; 2017

Capillaryzone electrophoresis (CZE) is a separative analytical technique providing alsothe electrophoretic mobility value of electrically charged macromolecules insolutions with well-defined pH, ionic strength, temperature, electricalpermittivity and viscosity. In this work experimental electrophoretic mobilityof peptides reported in the literature were used to apply and extend a model [1]able to characterize polypeptides chains through physicochemical propertieslike: equivalent Stokes hydrodynamic radius, asphericity, hydration, effectivecharge number, among others. From them it is possible to evaluate theelectrokinetic potential and the conformational chain fractals [1]. Theknowledge of these global properties is useful to understand key mechanisms ofmany application systems found in biotechnology, pharmacology and clinicalmedicine, among other disciplines. In these regards, it is interesting to pointout that most of the CZE studies of polypeptides reported in the literature maybe interpreted within the fundamental framework of well-established physicochemicaltheories, like the classical asymptotic Henry solution for low electrokinetic(zeta) potential of charged particles. In this work peptides with sizes lessthan 5 nm are studied. It is found that they satisfy the Hückel asymptotecorresponding to low electrokinetic potentials. Here we show that theSmoluchowski asymptote is not applicable to these polyampholyte particles. Furtherone may observe that in order to model the effective electrophoretic mobilityof peptides with high electrical charge numbers (high electrokineticpotentials) additional phenomena must be considered which are still under studyin the literature [2, 3]. Itis also important to point out that the peptides under study validate ourprevious findings indicating that the charge regulation phenomenon yields anear molecule pH shifted toward the pI, evaluated in relation to the bulk pH [1].In the present framework critical comparisons of different studies published onthis subject are provided