Figure 1. Schematic representation of DQ-Red BSA cargo uptake and processing in cells.

DQ-Red BSA is endocytosed in cells and traffics through early endosomes to late endosomes which then fuse with acidic hydrolase containing lysosomes. This leads to the formation of endo-lysosomes that degrade DQ-Red BSA, de-quenching the fluorescence of the dye attached to this cargo. DQ-Red BSA is heavily labeled with fluorescent dyes that lead to quenching of their fluorescence (shown by pink fluorophores attached to the cargo). Once DQ-Red BSA has reached the degradative endo-lysosomes, the cargo is broken down into smaller fragments which lead to the de-quenching of the fluorophores (shown as bright red spots in endo-lysosomes).