Tuning the conformations of hemoglobin via interactions with single-chain and Gemini quaternary ammonium surfactants

•All surfactants have enhancement effects on intrinsic fluorescence of Hb.•Different surfactant concentrations lead to different types of interaction modes.•Gemini surfactants have much strong binding ability with Hb than single-chain surfactants.•Interactions cause the transition of secondary structure of protein.