Analysis of Membrane Proteins by Two-Dimensional Gels
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Separation of a protein mixture by two-dimensional (2-D) gel electrophoresis is usually the first step of a proteomic analysis. The second step is the protein identification by mass spectrometry techniques, mainly by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Two-dimensional electrophoresis comprises two steps (dimensions): (1) separation of the proteins on the basis of differences in their net charge, called isoelectric focusing (IEF), which is usually performed on immobilized pH gradient (IPG) strips; and (2) separation of the focused proteins on the basis of differences in their molecular masses, which is performed in sodium dodecyl sulfate (SDS) polyacrylamide gels. The major advantage of 2-D electrophoresis is that it enables the simultaneous separation and visualization of thousands of unknown protein forms. No other method can do that at the present time. On the other hand, protein detection in 2-D gels is limited because (1) the major components of a protein mixture are usually visualized and (2) the detection of the low- and high-molecular-mass proteins, as well as of the basic and hydrophobic proteins, is inefficient.
KeywordsSodium Dodecyl Sulfate Acrylamide Solution Lithium Dodecyl Sulfate Zwitterionic Detergent Lithium Dodecyl Sulfate
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