Coomassie blue-stained 2D BN/SDS-PAGE separation of membrane protein complexes of C. thermocellum. Approximately 40 μg of protein was loaded in the first dimensional BN-PAGE lane. Sizes of molecular mass markers are indicated on the top of BN-P|AGE gel and at the left of the SDS gel. The slice of first dimensional BN-PAGE separation gel was placed on top of the second dimensional SDS-PAGE gel and resolved. Protein spots picked for mass spectrometry analysis are marked by arrows and numbered.