A turning point in proteome analysis: Sample prefractionation via multicompartment electrolyzers with isoelectric membranes

Sample prefractionation, as obtained via multicompartment electrolyzers wit h isoelectric membranes, greatly enhanced the load ability, resolution and detection sensitivity of two-dimensional (2-D) maps in proteome analysis. T his was demonstrated with different samples. In an Escherichia coil total c ell extract, analysis by a 2-D map run in a pH 4-5 gradient showed many mor e spots when prefractionated, as compared with standard maps available in d atabases such as SWISS-2DPAGE. Analysis of human plasma in the pH 3-6 range showed an increase in the number of highly acidic proteins in the fraction ated sample compared to whole plasma. With both samples no protein precipit ation or smears occurred and much larger sample amounts could be loaded upo n prefractionation, so that a large number of spots could be visualized by Coomassie staining, which is fully compatible with subsequent matrix assist ed laser desorption/ionization-time of flight (MALDI-TOF) analysis.