Blue native Electrophoresis is a "charge shift" method developed for isolation of native membrane protein complexes from biological membranes that also separates both acidic and basic water-soluble proteins at a fixed pH of 7.5. In combination with a second dimension sodium dodecylsulfate electrophoresis it provides an analytical method for the determination of molecular mass and oligomeric state of nondissociated complexes, of subunit composition, and of degree of purity and for the detection of subcomplexes. The method was applied to analysis of cytochrome bc/bf complexes. By combination of a novel colorless native polyacrylamide gel electrophoresis (CN-PAGE) with blue native BN-PAGE, a two-dimensional native technique was developed that is suitable for preparation of highly pure membrane protein complexes.