Immunoblotting Measurement of Cytochrome c Oxidase in Differentiated and Undifferentiated RGC-5 Mitochondria. RGC-5 cells were differentiated with staurosporine. Isolated mitochondrial samples from undifferentiated and differentiated mitochondria standardized for protein content were compared to corresponding mitochondria depleted samples for the presence of the mitochondrial transmembrane protein cytochrome c oxidase (COX), complex IV. Samples were immunoblotted with antibody to subunit 1 of complex IV. There was considerable purification of mitochondria compared to the mitochondria depleted samples for differentiated and undifferentiated RGC-5 cells. Differentiated RGC-5 cells had 2.5 times more cytochrome c oxidase than undifferentiated RGC-5 cells.