Mass analysis of a distinct peptide from the L4R protein using Method 1 (SDS-PAGE + LC-ESI-Q-TOF MS) Panel A shows the Coomassie blue stained SDS-PAGE gel of the core-enriched fraction and panel B is the membrane-enriched fraction. Gel slices that were analyzed by MS are denoted with letters. The full scan mass spectrum (inset of C) displays a doubly charged parent ion at m/z 867.9. The corresponding tandem mass spectrum (C) identifies a peptide of the L4R protein. Asterisks (*) denote the loss of ammonia (NH3) or water (H2O).