Properties of flavin fluorescence signal from an hrCN gel of DDM-solubilized brain mitochondria.A, time dependence of the upper KGDHC and lower complex I (gray and black circles, respectively) flavin-containing bands (as in Fig. 1) after 20% SDS was applied on the gel surface and repetitive fluorescent scans performed, protein load 40 μg. B, representative fluorescence image of an SDS-treated hrCN gel showing flavin fluorescence intensity at different protein loads (13–74 μg per well from left to right). C, dependence of the fluorescence intensity of the KGDHC and complex I bands upon protein load on the gel. Values are mean ± SEM (n = 4). D, calibration curve for quantitative analysis made of standard FMN solution applied directly on the gel surface and intensity of fluorescent spots measured (mean ± SEM, n = 3). DDM, n-dodecyl-β-d-maltoside; KGDHC, α-ketoglutarate dehydrogenase complex.