MONITORING POLYELECTROLYTE MOBILITY BY GEL-ELECTROPHORESIS

Electrophoretic methods are applied to studies of probe chain motion in gels, exploiting free solution measurements of the same motion to isolate gel matrix effects. Trends observed for gels, particularly in relationships between mobility and chain length and between mobility and chain topology, support a three state entanglement depiction, each state characterized by its own chain transport mechanism. These include excluded volume (unentangled regime), entropic barriers (weakly entangled regime), and reptation (strongly entangled regime). Intermediate entanglement provides the best fractionation, and evidence is presented that spatial variations in chain entropy control motion whenever the probe size approximately matches the gel mesh spacing. The backbone charge density, potentially an uncontrolled variable for synthetic samples, is shown to exert negligible influence on the mobility of highly charged probe molecules.