SDS–PAGE and deconvoluted FTICR-MS of protein samples. (a) Coomassie-stained SDS–PAGE of proteins before and after modification. Lane 2, native lysozyme; lane 3, modified lysozyme; lane 4, modified lysozyme after HIC purification; lane 5, native EfsQnr; lane 6, modified EfsQnr; lane 7, modified EfsQnr after HIC purification. Lanes 1 and 8, 10–150 kDa molecular-weight markers. (b, c) FTICR-MS of EfsQnr before (b) and after (c) modification by glutaraldehyde. (d, e) FTICR-MS of lysozyme before (d) and after modification (e) by glutaraldehyde. The measured masses are indicated.