The recombinant wild-type DC-SIGN (no dye labeling) was also expressed and purified, to investigate DC-SIGN binding to Gx-psDiMan using dynamic light scattering (DLS) and ITC. Protein concentration was determined from its UV absorbance at 280 nm using an extinction coefficient of 2.82 × 10 5 M -1 cm -1 (tetramer) as reported previously. 20, 27