Off-Gel Isoelectric Focusing


The 3100 OFFGEL Fractionator is used for the separation and fractionation of proteins and peptides by isoelectric focusing (IEF). The instrument can be used to (i) fractionate proteins and peptides prior to downstream analytical methods such as liquid chromatography coupled mass spectrometry (LC-MS), (ii) purify peptides, proteins or protein complexes and (iii) separate proteins by isoelectric focusing as the first dimension in classical 2-dimesnional gel electrophoresis. It can be operated in “off-gel” mode for an efficient in solution fractionation/separation or “in-gel” mode for conventional IEF. It operates two trays with 10 lanes each which are controlled by two independent power supplies. Each lane has an independent current/voltage reading for monitoring the electrophoretic mobility in individual samples. In off-gel mode samples can be collected into 13 or 24 fractions. We routinely use off-gel IEF for the pre-fractionating of complex iTRAQ labelled samples prior to LC-MS/MS and could increase the number of protein identifications by more than 3 fold compared to SCX/RP-uHPLC-based 2-D LC-coupled MS/MS.