Fractionation of complex protein mixtures by liquid-phase isoelectric focusing.

Protein fractionation is essential to uncovering low-abundance proteins in complex protein mixtures. Many common methods and techniques are used to fractionate proteins, including chromatography (size exclusion, affinity, ion exchange, etc.), electrophoresis, and solution chemistry. Regardless of the method employed, the ultimate goal of protein fractionation is to enable more protein analysis by today's current proteomics technologies, such as one- (1-DGE) or two-dimensional gel electrophoresis (2-DGE) and liquid-chromatography and tandem mass spectrometry (LC-MS/MS).The MicroRotofor isoelectric focusing (IEF) cell fractionates proteins in free solution according to their isoelectric point (pI). We demonstrate the ability of the MicroRotofor to enrich low-abundance proteins in mouse brain tissue, thus enabling further identification of potential biomarker candidates.