(A) Schematic diagram shows fluorescence dequenching assays. When the SRB-labeled liposomes are mixed with DiD-labeled influenza virus and fusion is triggered by low pH, the liposomal content leakage and transfer release the water-soluble SRB dyes and the weakening quenching effect results in the increase in the fluorescence intensity of SRB dye. When the lipid mixing commences, the lipophilic DiD dyes disperse over a larger membrane area and the fluorescence signal of DiD also increases. (B) Fluorescence intensity of SRB (yellow, solid curve), reporting liposomal content leakage and transfer, and DiD (blue, dashed curve), reporting membrane merging, is monitored over time. Completely dequenching is achieved in the presence of 1 % (v/v) TritonX-100 detergent.