To check whether DC-SIGN/R binding with Gx-DiMan is reversible, the Dhs of Gx-DiMan+DC-SIGN/R complexes were monitored by switching the solution pH between pH 7. Fig. revealed that, upon switching pH from 7.4 to 5.0, there was a rapid increase of the Dhs for both DC-SIGN/R-Gx-DiMan complexes, while switching pH back from 5.0 to 7.4 led to a rapid decrease of Dh. This result was fully consistent to that observed in the previous section (Fig. ), which also gave much larger lectin-GNP assemblies at pH 5.0 than that at pH 7.4, especially for DC-SIGN (Fig. ). The small Dh at pH 7.4 was fully consistent to DC-SIGN's tetravalent binding with one GNP-DiMan at pH 7.4 as observed previously. The pH-dependent Dh switching between pH 5.0 and 7.4 was reversible for both DC-SIGN and DC-SIGNR, and that with G13-DiMan appeared to have better reversibility than that with G27-DiMan, especially with DC-SIGN. In all cases, the Dh values of the lectin-Gx-DiMan assemblies were stabilised at ∼30 mins after each pH switching, in both pH down and up directions. This result indicates that 30 min is required to achieve the desired lectin-Gx-DiMan assemblies or dis-assemblies under our experimental conditions. This result is also consistent for DC-SIGN's biological role of an endocytic and recycling receptor: it binds strongly to endocytose the target ligands at normal physiological pH, and then releases the ligands under the acidic environment of early to late endosomes so that it can be recycled back to cell surface for further binding and endocytosis of more ligands. It should be noted that, while switching pH from 5.0 to 7.4 generally produced smaller assemblies (smaller Dhs), the stabilised Dhs for the DC-SIGN/R-Gx-DiMan complexes were still larger than those directly prepared at pH 7.4 (especially for G27-DiMan). This indicated that only partial restoration of the original Gx-DiMan-DC-SIGN complexes was achieved within 30 mins.