The numbers of glycan ligands on each GNP (i.e., glycan valency) were estimated from the ligand amount difference between that added and that remained unbound in the supernatant after GNP conjugation via a phenol-sulphuric acid carbohydrate quantification method as described previously 11, 19, 48 (see SI, Table ). The average inter-glycan distance (d) was estimated from their Dh value and glycan valency using the method reported previously, giving d values of ∼0.95, ∼0.93 and ∼0.80 nm for G5-, G13-and G27-DiMan100%, respectively (SI, Table ). These d values match well to the majority of inter-glycan sequon spaces (e.g. 0.7-1.3 nm) found on the HIV surface glycoprotein gp160 trimer. Therefore, our Gx-glycans are good mimics for probing the gp160-DC-SIGN interactions which are responsible for mediating the HIV infections.