This result further supports our conclusion of the tetravalent binding mode for DC-SIGN described in the previous section. The good agreement of ΔH 0 values obtained here with those measured in ITC suggests that our GNP fluorescence quenching can act as a reliable new method for probing DC-SIGN MLGI thermodynamics. (2) The ΔS 0 values for Gx-DiMan-DC-SIGN binding were found to reduce gradually with the increasing GNP scaffold size. The total MLGI entropy changes reflect the net contributions of the binding induced changes in translational, rotational, and conformational entropies of lectins and Gx-DiMan ligands as well as their surrounding media (e.g. binding buffer). Therefore, a likely reason for the reduced entropic penalty for the bigger GNPs observed here could be due to the presence of more free, unbound DiMan ligands on their surfaces (measurements performed at PGRs below surface saturation) which are flexible (anchored to the GNP surface via hydrophilic, flexible EG4 linkers), and thus they have largely retained their conformational and rotational degrees of freedom. Taking together, the thermodynamic data of DC-SIGN-Gx-DiMan binding obtained here are consistent to that expected for DC-SIGN based on its simultaneous tetravalent binding mode described in the earlier sections.