For DC-SIGNR, the average Dhs of its complex with Gx-DiMan were found to generally increase with the decreasing pH from 7.4 to 4.6, although significant differences in the distribution species were also noticeable. For example, small individual G13-DiMan particles and large DC-SIGNR-G13-DiMan assembles were found to coexist at pH 7.4, likely due to DC-SIGNR's relatively weak affinity was unable to fully crosslink with all G13-DiMan particles (Fig. ). As pH was reduced, the amounts of aggregated species increased while that of isolated single particle species decreased. As pH was lowered to 6.2 and below, only a single large aggregated species was observed (pH 6.2 to 5.0), indicating highly efficient DC-SIGNR-G13-DiMan crosslinking. This result is consistent to the strong DC-SIGNR affinity for G13-DiMan (high QE) over this pH range (Fig. ). Further reducing pH to 4.6 produced two different Dh species, signifying partial dissociation of DC-SIGNR-G13-DiMan complexes (Fig. , and SI, Fig. ), which agreed well to their reduced affinity (QE, see Fig. ). Overall, these results agreed well to the inverted V-shaped QE-pH dependence observed in fluorescence quenching experiment, where DC-SIGNR displayed the highest affinity (QE) at pH 5.4. In general, the average Dhs of DC-SIGNR-Gx-DiMan complexes were significantly greater than that expected for single Gx-DiMan particles coated with a monolayer of DC-SIGNR molecules, especially for G27-DiMan, indicating that they were formed by GNP-lectin crosslinking. These results matched well to that expected for DC-SIGNR based on its crosslinking binding mode with GNP-DiMan observed previously at pH 7.4. Interestingly, the consistently small Dhs for G13-DiMan-DC-SIGN complexes observed over pH 7.4 to 5.8 also matched well to their consistently stable QE over this pH range (Fig. ). Moreover, a significantly increased Dh at the more acidic pH environment (e.g. pH 5.4 to 4.6) also matched well to the reduced fluorescence QEs observed for DC-SIGN under such low pHs. This result indicated that the pH-dependent fluorescence QE and Dh size appeared to be negatively correlated (i.e. small lectin-GNP assemblies gave high QE for DC-SIGN). The DLS and fluorescence quenching results suggested that low pH media are likely to cause conformational changes in DC-SIGN/R and/or alter their binding modes, reducing their MLGI affinities to trigger the release of bound glycan ligands. Our results thus revealed that the acidic intracellular endosomes or lysosomes may cause glycan ligands to be released from their DC-SIGN/R complexes during the natural trafficking processes. The different Gx-DiMan affinity -pH dependences between DC-SIGN and DC-SIGNR may be associated with their different functions in the transmission of virus infections.