protein sequence identification Identification by mass spectrometry multidimensional protein identification technology MudPIT is a method for rapid and large-scale protein identification by multidimensional liquid chromatography associated with tandem mass spectrometry. The chromatography step consists of strong cation exchange material back-to-back with reversed phase material inside fused silica capillaries. The peptides bound to the cation-exchange resin are freed by the gradually increasing salt concentration of the buffer and are subsequently retained by the reversed phase resin. Increasing buffers hydrophobicity progressively elute peptides from the reversed phase packing directly into the mass spectrometer. Typically this mass spectrometer will be a tandem electrospray, so peptides undergo ionization in the liquid phase, are separated in a primary mass spectrometer, analysed in the second mass spectrometer and identified. MI:0658 PSI-MI mudpit confirmation by molecular weight