Where IF0 and IF are the integrated fluorescence of labelled DC-SIGN in the absence and presence of 1 molar equivalent of Gx-psDiMan, respectively. GNP can efficiently quench a wide range of fluorophores via a nano surface energy transfer (NSET) mechanism (QE is proportional to the inverse 4 th power of separation distance, d, i.e., QE = 1/[1 + (d/d0) 4 ], where d0 is the separation distance giving 50% quenching). Fluorescence quenching via the NSET mechanism is more effective and covers a greater distance range than organic quenchers based on the Förster resonance energy transfer (FRET, where QE is proportional to the inverse 6 th power of dye-quencher distance, R, QE = 1/[1 + (R/R0) ) mechanism. Moreover, a GNP has been shown to quench fluorescence by up to 99.97% in a closed DNA hairpin structure. Therefore, it is safe to assume that the measured QE% here represents the percentage of lectins that are bound to Gx-psDiMan. Thus, the apparent binding equilibrium dissociation constant (Kd) can be derived from the QE-C relationship by fitting with the Hill's equation (2): 14