Protein/Peptide Fractionation

Strong cation exchange HPLC separation of peptides is performed on an Applied Biosystems Vision Workstation. This system uses a 2.1x 200mm PolySULFOETHYL A™ column (PolyLC Inc.) with a linear 118 minute gradient (Buffer A: 10mM potassium phosphate, 25% acetonitrile pH 3.0 and Buffer B: 10mM potassium phosphate, 25% acetonitrile pH 3.0, plus 1M potassium chloride). Each cation-exchange fraction (normally 20 fractions) is dried and re-suspended in 5ul 70% formic acid, diluted to 15µl with 0.1% TFA prior to loading onto the LTQ Orbitrap system.