Elucidation of pectin methylester distributions by capillary electrophoresis

Evidence is presented that the electrophoretic mobility of the polysaccharide pectin in typical capillary electrophoresis (CE) experiments is determined largely by its chain-averaged charge density, irrespective of how that charge is distributed. This was found to be the case for both high and low calcium sensitive sister fractions separated from a mother sample on the grounds of calcium affinity and for blocky methylester distributions generated by a processive demethylating enzyme. The blockiness of the generated intramolecular methylester distribution was substantiated experimentally, also by CE, by observing the oligomeric digest fragments produced by incubation with endo-polygalacturonase II from Aspergillus niger. The conclusion that the CE migration time is largely invariant to the intramolecular methylester distribution supports the idea that the CE peak shapes can be used to give a useful indication of the intermolecular methylester distribution.