Cacl2 2h2o

MgCl2•6H2O (98%), NaCl (98%), NaClO4•H2O (98%), NaF (99%), Mg(NO3)2•6H2O, KSCN (99%), LiNO3 (99%) and D2O (99.9 atom% D) were obtained from Sigma-Aldrich (Diegem, Belgium). CaCl2•2H2O (99.5%), NaNO3 (99%), Na2SO4 (99%), Ca(NO3)2•4H2O (99%), KNO3 (99%), NH4NO3 (99%) and HNO3 (65%) were purchased from Chem-Lab (Zedelgem, Belgium). KCl (99.5%) and NaI (99.5%) were purchased from AppliChem (Darmstadt, Germany) and LiCl (99%) from Fisher Chemical (Loughborough, UK). CsCl (99%), NaBr (99.5%), NH4Cl (99.5%), H2SO4 (96%), HClO4 (70%), HCl (37%) and 1,4-dioxane (99.9%) were obtained from Acros Organics (Geel, Belgium). The silicone solution in isopropanol was purchased from SERVA Electrophoresis GmbH (Heidelberg, Germany). All chemicals were used as received without further purification.

Citrus pectin with a high degree of methylesterification (DM of 82.2 ± 1.2%) was purchased from Sigma-Aldrich (Diegem, Belgium) and used as a starting material to prepare pectin samples with low and intermediate degrees of methylesterification by enzymatic demethylesterification.
Fresh carrots (Daucus carota cv Nerac) were purchased from a local supermarket and stored at 4 °C until use. For isolation of carrot pectin methylesterase (PME), the carrots were peeled, cut into 1 cm 3 cubes and PME was extracted and purified with PME inhibitor (PMEI) from kiwi fruit as described by Jolie et al. (2009) . PME activity was determined prior to use in demethylesterification of pectin (Ly-Nguyen et al., 2002) .
All chemicals and reagents used were of analytical grade and were purchased from Sigma Aldrich (Diegem, Belgium) except for KCl, MgCl2.6H2O, NaOH, methanol (Acros Organics, Geel, Belgium); KH2PO4; NaHCO3, NaCl, H2SO4 (Fisher Scientific, Merelbeke, Belgium); HCl (VWR, Leuven, Belgium); CaCl2.2H2O (Chem-Lab, Zedelgem, Belgium). Pancreatin was kindly donated by Nordmark (Saeby, Denmark). Ultrapure water (organic free, 18.2 MΩ cm resistance) was supplied by a Simplicitiy TM water purification system (Millipore, Billerica, USA) and was used for all experiments.