Emission spectra over 650-800 nm were collected with excitation and emission slit widths of 5 nm under a slow scan speed. All measurements were carried out in a binding buffer (20 mM HEPES, pH 7.8, 100 mM NaCl, 10 mM CaCl2) containing 1 mg/mL BSA to reduce any non-specific interactions and absorption to cuvette walls. The required amounts of Gx-DiMan and DC-SIGN/R were mixed and then incubated at RT for 20 mins before recording their fluorescence spectra. The fluorescence spectra from 650 to 800 nm were integrated and used to calculate the quenching efficiency (QE).